@sveltejs/kit/hooks
import { function sequence(...handlers: Handle[]): HandleA helper function for sequencing multiple handle calls in a middleware-like manner.
The behavior for the handle options is as follows:
transformPageChunk is applied in reverse order and merged
preload is applied in forward order, the first option "wins" and no preload options after it are called
filterSerializedResponseHeaders behaves the same as preload
src/hooks.serverimport { sequence } from '@sveltejs/kit/hooks';
/// type: import('@sveltejs/kit/hooks').Handle
async function first({ event, resolve }) {
console.log('first pre-processing');
const result = await resolve(event, {
transformPageChunk: ({ html }) => {
// transforms are applied in reverse order
console.log('first transform');
return html;
},
preload: () => {
// this one wins as it's the first defined in the chain
console.log('first preload');
return true;
}
});
console.log('first post-processing');
return result;
}
/// type: import('@sveltejs/kit/hooks').Handle
async function second({ event, resolve }) {
console.log('second pre-processing');
const result = await resolve(event, {
transformPageChunk: ({ html }) => {
console.log('second transform');
return html;
},
preload: () => {
console.log('second preload');
return true;
},
filterSerializedResponseHeaders: () => {
// this one wins as it's the first defined in the chain
console.log('second filterSerializedResponseHeaders');
return true;
}
});
console.log('second post-processing');
return result;
}
export const handle = sequence(first, second);
The example above would print:
first pre-processing
first preload
second pre-processing
second filterSerializedResponseHeaders
second transform
first transform
second post-processing
first post-processing
Calling resolve invokes the next handler in the sequence (or SvelteKit itself, if it is the last one). To pass data between handlers, use event.locals.
sequence } from '@sveltejs/kit/hooks';sequence
A helper function for sequencing multiple handle calls in a middleware-like manner.
The behavior for the handle options is as follows:
transformPageChunkis applied in reverse order and mergedpreloadis applied in forward order, the first option "wins" and nopreloadoptions after it are calledfilterSerializedResponseHeadersbehaves the same aspreload
import { function sequence(...handlers: Handle[]): HandleA helper function for sequencing multiple handle calls in a middleware-like manner.
The behavior for the handle options is as follows:
transformPageChunk is applied in reverse order and merged
preload is applied in forward order, the first option "wins" and no preload options after it are called
filterSerializedResponseHeaders behaves the same as preload
src/hooks.serverimport { sequence } from '@sveltejs/kit/hooks';
/// type: import('@sveltejs/kit/hooks').Handle
async function first({ event, resolve }) {
console.log('first pre-processing');
const result = await resolve(event, {
transformPageChunk: ({ html }) => {
// transforms are applied in reverse order
console.log('first transform');
return html;
},
preload: () => {
// this one wins as it's the first defined in the chain
console.log('first preload');
return true;
}
});
console.log('first post-processing');
return result;
}
/// type: import('@sveltejs/kit/hooks').Handle
async function second({ event, resolve }) {
console.log('second pre-processing');
const result = await resolve(event, {
transformPageChunk: ({ html }) => {
console.log('second transform');
return html;
},
preload: () => {
console.log('second preload');
return true;
},
filterSerializedResponseHeaders: () => {
// this one wins as it's the first defined in the chain
console.log('second filterSerializedResponseHeaders');
return true;
}
});
console.log('second post-processing');
return result;
}
export const handle = sequence(first, second);
The example above would print:
first pre-processing
first preload
second pre-processing
second filterSerializedResponseHeaders
second transform
first transform
second post-processing
first post-processing
Calling resolve invokes the next handler in the sequence (or SvelteKit itself, if it is the last one). To pass data between handlers, use event.locals.
sequence } from '@sveltejs/kit/hooks';
/** @type {import('@sveltejs/kit/hooks').Handle} */
async function function first(input: {
event: RequestEvent;
resolve: (event: RequestEvent, opts?: ResolveOptions) => Promise<Response>;
}): MaybePromise<Response>
first({ event: RequestEvent<Record<string, string>, string | null>event, resolve: (event: RequestEvent, opts?: ResolveOptions) => Promise<Response>resolve }) {
var console: ConsoleThe console module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:
- A
Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
- A global
console instance configured to write to process.stdout and
process.stderr. The global console can be used without importing the node:console module.
Warning: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the note on process I/O for
more information.
Example using the global console:
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
// Error: Whoops, something bad happened
// at [eval]:5:15
// at Script.runInThisContext (node:vm:132:18)
// at Object.runInThisContext (node:vm:309:38)
// at node:internal/process/execution:77:19
// at [eval]-wrapper:6:22
// at evalScript (node:internal/process/execution:76:60)
// at node:internal/main/eval_string:23:3
const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
Example using the Console class:
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);
myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err
const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
console.Console.log(message?: any, ...optionalParams: any[]): void (+1 overload)Prints to stdout with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to printf(3)
(the arguments are all passed to util.format()).
const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
See util.format() for more information.
log('first pre-processing');
const const result: Responseresult = await resolve: (event: RequestEvent, opts?: ResolveOptions) => Promise<Response>resolve(event: RequestEvent<Record<string, string>, string | null>event, {
ResolveOptions.transformPageChunk?: ((input: {
html: string;
done: boolean;
}) => MaybePromise<string | undefined>) | undefined
Applies custom transforms to HTML. If done is true, it's the final chunk. Chunks are not guaranteed to be well-formed HTML
(they could include an element's opening tag but not its closing tag, for example)
but they will always be split at sensible boundaries such as %sveltekit.head% or layout/page components.
transformPageChunk: ({ html: stringhtml }) => {
// transforms are applied in reverse order
var console: ConsoleThe console module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:
- A
Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
- A global
console instance configured to write to process.stdout and
process.stderr. The global console can be used without importing the node:console module.
Warning: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the note on process I/O for
more information.
Example using the global console:
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
// Error: Whoops, something bad happened
// at [eval]:5:15
// at Script.runInThisContext (node:vm:132:18)
// at Object.runInThisContext (node:vm:309:38)
// at node:internal/process/execution:77:19
// at [eval]-wrapper:6:22
// at evalScript (node:internal/process/execution:76:60)
// at node:internal/main/eval_string:23:3
const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
Example using the Console class:
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);
myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err
const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
console.Console.log(message?: any, ...optionalParams: any[]): void (+1 overload)Prints to stdout with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to printf(3)
(the arguments are all passed to util.format()).
const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
See util.format() for more information.
log('first transform');
return html: stringhtml;
},
ResolveOptions.preload?: ((input: {
type: "font" | "css" | "js" | "asset";
path: string;
}) => boolean) | undefined
Determines which files should be preloaded. Files are preloaded via <link> tags added to the
<head> tag; if output.linkHeaderPreload is enabled, dynamically rendered pages use the
Link response header instead.
By default, js and css files will be preloaded.
preload: () => {
// this one wins as it's the first defined in the chain
var console: ConsoleThe console module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:
- A
Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
- A global
console instance configured to write to process.stdout and
process.stderr. The global console can be used without importing the node:console module.
Warning: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the note on process I/O for
more information.
Example using the global console:
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
// Error: Whoops, something bad happened
// at [eval]:5:15
// at Script.runInThisContext (node:vm:132:18)
// at Object.runInThisContext (node:vm:309:38)
// at node:internal/process/execution:77:19
// at [eval]-wrapper:6:22
// at evalScript (node:internal/process/execution:76:60)
// at node:internal/main/eval_string:23:3
const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
Example using the Console class:
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);
myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err
const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
console.Console.log(message?: any, ...optionalParams: any[]): void (+1 overload)Prints to stdout with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to printf(3)
(the arguments are all passed to util.format()).
const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
See util.format() for more information.
log('first preload');
return true;
}
});
var console: ConsoleThe console module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:
- A
Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
- A global
console instance configured to write to process.stdout and
process.stderr. The global console can be used without importing the node:console module.
Warning: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the note on process I/O for
more information.
Example using the global console:
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
// Error: Whoops, something bad happened
// at [eval]:5:15
// at Script.runInThisContext (node:vm:132:18)
// at Object.runInThisContext (node:vm:309:38)
// at node:internal/process/execution:77:19
// at [eval]-wrapper:6:22
// at evalScript (node:internal/process/execution:76:60)
// at node:internal/main/eval_string:23:3
const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
Example using the Console class:
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);
myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err
const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
console.Console.log(message?: any, ...optionalParams: any[]): void (+1 overload)Prints to stdout with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to printf(3)
(the arguments are all passed to util.format()).
const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
See util.format() for more information.
log('first post-processing');
return const result: Responseresult;
}
/** @type {import('@sveltejs/kit/hooks').Handle} */
async function function second(input: {
event: RequestEvent;
resolve: (event: RequestEvent, opts?: ResolveOptions) => Promise<Response>;
}): MaybePromise<Response>
second({ event: RequestEvent<Record<string, string>, string | null>event, resolve: (event: RequestEvent, opts?: ResolveOptions) => Promise<Response>resolve }) {
var console: ConsoleThe console module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:
- A
Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
- A global
console instance configured to write to process.stdout and
process.stderr. The global console can be used without importing the node:console module.
Warning: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the note on process I/O for
more information.
Example using the global console:
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
// Error: Whoops, something bad happened
// at [eval]:5:15
// at Script.runInThisContext (node:vm:132:18)
// at Object.runInThisContext (node:vm:309:38)
// at node:internal/process/execution:77:19
// at [eval]-wrapper:6:22
// at evalScript (node:internal/process/execution:76:60)
// at node:internal/main/eval_string:23:3
const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
Example using the Console class:
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);
myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err
const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
console.Console.log(message?: any, ...optionalParams: any[]): void (+1 overload)Prints to stdout with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to printf(3)
(the arguments are all passed to util.format()).
const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
See util.format() for more information.
log('second pre-processing');
const const result: Responseresult = await resolve: (event: RequestEvent, opts?: ResolveOptions) => Promise<Response>resolve(event: RequestEvent<Record<string, string>, string | null>event, {
ResolveOptions.transformPageChunk?: ((input: {
html: string;
done: boolean;
}) => MaybePromise<string | undefined>) | undefined
Applies custom transforms to HTML. If done is true, it's the final chunk. Chunks are not guaranteed to be well-formed HTML
(they could include an element's opening tag but not its closing tag, for example)
but they will always be split at sensible boundaries such as %sveltekit.head% or layout/page components.
transformPageChunk: ({ html: stringhtml }) => {
var console: ConsoleThe console module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:
- A
Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
- A global
console instance configured to write to process.stdout and
process.stderr. The global console can be used without importing the node:console module.
Warning: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the note on process I/O for
more information.
Example using the global console:
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
// Error: Whoops, something bad happened
// at [eval]:5:15
// at Script.runInThisContext (node:vm:132:18)
// at Object.runInThisContext (node:vm:309:38)
// at node:internal/process/execution:77:19
// at [eval]-wrapper:6:22
// at evalScript (node:internal/process/execution:76:60)
// at node:internal/main/eval_string:23:3
const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
Example using the Console class:
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);
myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err
const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
console.Console.log(message?: any, ...optionalParams: any[]): void (+1 overload)Prints to stdout with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to printf(3)
(the arguments are all passed to util.format()).
const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
See util.format() for more information.
log('second transform');
return html: stringhtml;
},
ResolveOptions.preload?: ((input: {
type: "font" | "css" | "js" | "asset";
path: string;
}) => boolean) | undefined
Determines which files should be preloaded. Files are preloaded via <link> tags added to the
<head> tag; if output.linkHeaderPreload is enabled, dynamically rendered pages use the
Link response header instead.
By default, js and css files will be preloaded.
preload: () => {
var console: ConsoleThe console module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:
- A
Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
- A global
console instance configured to write to process.stdout and
process.stderr. The global console can be used without importing the node:console module.
Warning: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the note on process I/O for
more information.
Example using the global console:
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
// Error: Whoops, something bad happened
// at [eval]:5:15
// at Script.runInThisContext (node:vm:132:18)
// at Object.runInThisContext (node:vm:309:38)
// at node:internal/process/execution:77:19
// at [eval]-wrapper:6:22
// at evalScript (node:internal/process/execution:76:60)
// at node:internal/main/eval_string:23:3
const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
Example using the Console class:
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);
myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err
const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
console.Console.log(message?: any, ...optionalParams: any[]): void (+1 overload)Prints to stdout with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to printf(3)
(the arguments are all passed to util.format()).
const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
See util.format() for more information.
log('second preload');
return true;
},
ResolveOptions.filterSerializedResponseHeaders?: ((name: string, value: string) => boolean) | undefinedDetermines which headers should be included in serialized responses when a load function loads a resource with fetch.
By default, none will be included.
filterSerializedResponseHeaders: () => {
// this one wins as it's the first defined in the chain
var console: ConsoleThe console module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:
- A
Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
- A global
console instance configured to write to process.stdout and
process.stderr. The global console can be used without importing the node:console module.
Warning: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the note on process I/O for
more information.
Example using the global console:
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
// Error: Whoops, something bad happened
// at [eval]:5:15
// at Script.runInThisContext (node:vm:132:18)
// at Object.runInThisContext (node:vm:309:38)
// at node:internal/process/execution:77:19
// at [eval]-wrapper:6:22
// at evalScript (node:internal/process/execution:76:60)
// at node:internal/main/eval_string:23:3
const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
Example using the Console class:
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);
myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err
const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
console.Console.log(message?: any, ...optionalParams: any[]): void (+1 overload)Prints to stdout with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to printf(3)
(the arguments are all passed to util.format()).
const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
See util.format() for more information.
log('second filterSerializedResponseHeaders');
return true;
}
});
var console: ConsoleThe console module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:
- A
Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
- A global
console instance configured to write to process.stdout and
process.stderr. The global console can be used without importing the node:console module.
Warning: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the note on process I/O for
more information.
Example using the global console:
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
// Error: Whoops, something bad happened
// at [eval]:5:15
// at Script.runInThisContext (node:vm:132:18)
// at Object.runInThisContext (node:vm:309:38)
// at node:internal/process/execution:77:19
// at [eval]-wrapper:6:22
// at evalScript (node:internal/process/execution:76:60)
// at node:internal/main/eval_string:23:3
const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
Example using the Console class:
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);
myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err
const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
console.Console.log(message?: any, ...optionalParams: any[]): void (+1 overload)Prints to stdout with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to printf(3)
(the arguments are all passed to util.format()).
const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
See util.format() for more information.
log('second post-processing');
return const result: Responseresult;
}
export const const handle: Handlehandle = function sequence(...handlers: Handle[]): HandleA helper function for sequencing multiple handle calls in a middleware-like manner.
The behavior for the handle options is as follows:
transformPageChunk is applied in reverse order and merged
preload is applied in forward order, the first option "wins" and no preload options after it are called
filterSerializedResponseHeaders behaves the same as preload
src/hooks.serverimport { sequence } from '@sveltejs/kit/hooks';
/// type: import('@sveltejs/kit/hooks').Handle
async function first({ event, resolve }) {
console.log('first pre-processing');
const result = await resolve(event, {
transformPageChunk: ({ html }) => {
// transforms are applied in reverse order
console.log('first transform');
return html;
},
preload: () => {
// this one wins as it's the first defined in the chain
console.log('first preload');
return true;
}
});
console.log('first post-processing');
return result;
}
/// type: import('@sveltejs/kit/hooks').Handle
async function second({ event, resolve }) {
console.log('second pre-processing');
const result = await resolve(event, {
transformPageChunk: ({ html }) => {
console.log('second transform');
return html;
},
preload: () => {
console.log('second preload');
return true;
},
filterSerializedResponseHeaders: () => {
// this one wins as it's the first defined in the chain
console.log('second filterSerializedResponseHeaders');
return true;
}
});
console.log('second post-processing');
return result;
}
export const handle = sequence(first, second);
The example above would print:
first pre-processing
first preload
second pre-processing
second filterSerializedResponseHeaders
second transform
first transform
second post-processing
first post-processing
Calling resolve invokes the next handler in the sequence (or SvelteKit itself, if it is the last one). To pass data between handlers, use event.locals.
sequence(function first(input: {
event: RequestEvent;
resolve: (event: RequestEvent, opts?: ResolveOptions) => Promise<Response>;
}): MaybePromise<Response>
first, function second(input: {
event: RequestEvent;
resolve: (event: RequestEvent, opts?: ResolveOptions) => Promise<Response>;
}): MaybePromise<Response>
second);import { function sequence(...handlers: Handle[]): HandleA helper function for sequencing multiple handle calls in a middleware-like manner.
The behavior for the handle options is as follows:
transformPageChunk is applied in reverse order and merged
preload is applied in forward order, the first option "wins" and no preload options after it are called
filterSerializedResponseHeaders behaves the same as preload
src/hooks.serverimport { sequence } from '@sveltejs/kit/hooks';
/// type: import('@sveltejs/kit/hooks').Handle
async function first({ event, resolve }) {
console.log('first pre-processing');
const result = await resolve(event, {
transformPageChunk: ({ html }) => {
// transforms are applied in reverse order
console.log('first transform');
return html;
},
preload: () => {
// this one wins as it's the first defined in the chain
console.log('first preload');
return true;
}
});
console.log('first post-processing');
return result;
}
/// type: import('@sveltejs/kit/hooks').Handle
async function second({ event, resolve }) {
console.log('second pre-processing');
const result = await resolve(event, {
transformPageChunk: ({ html }) => {
console.log('second transform');
return html;
},
preload: () => {
console.log('second preload');
return true;
},
filterSerializedResponseHeaders: () => {
// this one wins as it's the first defined in the chain
console.log('second filterSerializedResponseHeaders');
return true;
}
});
console.log('second post-processing');
return result;
}
export const handle = sequence(first, second);
The example above would print:
first pre-processing
first preload
second pre-processing
second filterSerializedResponseHeaders
second transform
first transform
second post-processing
first post-processing
Calling resolve invokes the next handler in the sequence (or SvelteKit itself, if it is the last one). To pass data between handlers, use event.locals.
sequence } from '@sveltejs/kit/hooks';
import type { type Handle = (input: {
event: RequestEvent;
resolve: (event: RequestEvent, opts?: ResolveOptions) => Promise<Response>;
}) => MaybePromise<Response>
The handle hook runs every time the SvelteKit server receives a request and
determines the response.
It receives an event object representing the request and a function called resolve, which renders the route and generates a Response.
This allows you to modify response headers or bodies, or bypass SvelteKit entirely (for implementing routes programmatically, for example).
Handle } from '@sveltejs/kit/hooks';
const const first: Handlefirst: type Handle = (input: {
event: RequestEvent;
resolve: (event: RequestEvent, opts?: ResolveOptions) => Promise<Response>;
}) => MaybePromise<Response>
The handle hook runs every time the SvelteKit server receives a request and
determines the response.
It receives an event object representing the request and a function called resolve, which renders the route and generates a Response.
This allows you to modify response headers or bodies, or bypass SvelteKit entirely (for implementing routes programmatically, for example).
Handle = async ({ event: RequestEvent<Record<string, string>, string | null>event, resolve: (event: RequestEvent, opts?: ResolveOptions) => Promise<Response>resolve }) => {
var console: ConsoleThe console module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:
- A
Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
- A global
console instance configured to write to process.stdout and
process.stderr. The global console can be used without importing the node:console module.
Warning: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the note on process I/O for
more information.
Example using the global console:
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
// Error: Whoops, something bad happened
// at [eval]:5:15
// at Script.runInThisContext (node:vm:132:18)
// at Object.runInThisContext (node:vm:309:38)
// at node:internal/process/execution:77:19
// at [eval]-wrapper:6:22
// at evalScript (node:internal/process/execution:76:60)
// at node:internal/main/eval_string:23:3
const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
Example using the Console class:
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);
myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err
const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
console.Console.log(message?: any, ...optionalParams: any[]): void (+1 overload)Prints to stdout with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to printf(3)
(the arguments are all passed to util.format()).
const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
See util.format() for more information.
log('first pre-processing');
const const result: Responseresult = await resolve: (event: RequestEvent, opts?: ResolveOptions) => Promise<Response>resolve(event: RequestEvent<Record<string, string>, string | null>event, {
ResolveOptions.transformPageChunk?: ((input: {
html: string;
done: boolean;
}) => MaybePromise<string | undefined>) | undefined
Applies custom transforms to HTML. If done is true, it's the final chunk. Chunks are not guaranteed to be well-formed HTML
(they could include an element's opening tag but not its closing tag, for example)
but they will always be split at sensible boundaries such as %sveltekit.head% or layout/page components.
transformPageChunk: ({ html: stringhtml }) => {
// transforms are applied in reverse order
var console: ConsoleThe console module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:
- A
Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
- A global
console instance configured to write to process.stdout and
process.stderr. The global console can be used without importing the node:console module.
Warning: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the note on process I/O for
more information.
Example using the global console:
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
// Error: Whoops, something bad happened
// at [eval]:5:15
// at Script.runInThisContext (node:vm:132:18)
// at Object.runInThisContext (node:vm:309:38)
// at node:internal/process/execution:77:19
// at [eval]-wrapper:6:22
// at evalScript (node:internal/process/execution:76:60)
// at node:internal/main/eval_string:23:3
const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
Example using the Console class:
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);
myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err
const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
console.Console.log(message?: any, ...optionalParams: any[]): void (+1 overload)Prints to stdout with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to printf(3)
(the arguments are all passed to util.format()).
const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
See util.format() for more information.
log('first transform');
return html: stringhtml;
},
ResolveOptions.preload?: ((input: {
type: "font" | "css" | "js" | "asset";
path: string;
}) => boolean) | undefined
Determines which files should be preloaded. Files are preloaded via <link> tags added to the
<head> tag; if output.linkHeaderPreload is enabled, dynamically rendered pages use the
Link response header instead.
By default, js and css files will be preloaded.
preload: () => {
// this one wins as it's the first defined in the chain
var console: ConsoleThe console module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:
- A
Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
- A global
console instance configured to write to process.stdout and
process.stderr. The global console can be used without importing the node:console module.
Warning: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the note on process I/O for
more information.
Example using the global console:
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
// Error: Whoops, something bad happened
// at [eval]:5:15
// at Script.runInThisContext (node:vm:132:18)
// at Object.runInThisContext (node:vm:309:38)
// at node:internal/process/execution:77:19
// at [eval]-wrapper:6:22
// at evalScript (node:internal/process/execution:76:60)
// at node:internal/main/eval_string:23:3
const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
Example using the Console class:
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);
myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err
const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
console.Console.log(message?: any, ...optionalParams: any[]): void (+1 overload)Prints to stdout with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to printf(3)
(the arguments are all passed to util.format()).
const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
See util.format() for more information.
log('first preload');
return true;
}
});
var console: ConsoleThe console module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:
- A
Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
- A global
console instance configured to write to process.stdout and
process.stderr. The global console can be used without importing the node:console module.
Warning: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the note on process I/O for
more information.
Example using the global console:
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
// Error: Whoops, something bad happened
// at [eval]:5:15
// at Script.runInThisContext (node:vm:132:18)
// at Object.runInThisContext (node:vm:309:38)
// at node:internal/process/execution:77:19
// at [eval]-wrapper:6:22
// at evalScript (node:internal/process/execution:76:60)
// at node:internal/main/eval_string:23:3
const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
Example using the Console class:
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);
myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err
const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
console.Console.log(message?: any, ...optionalParams: any[]): void (+1 overload)Prints to stdout with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to printf(3)
(the arguments are all passed to util.format()).
const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
See util.format() for more information.
log('first post-processing');
return const result: Responseresult;
};
const const second: Handlesecond: type Handle = (input: {
event: RequestEvent;
resolve: (event: RequestEvent, opts?: ResolveOptions) => Promise<Response>;
}) => MaybePromise<Response>
The handle hook runs every time the SvelteKit server receives a request and
determines the response.
It receives an event object representing the request and a function called resolve, which renders the route and generates a Response.
This allows you to modify response headers or bodies, or bypass SvelteKit entirely (for implementing routes programmatically, for example).
Handle = async ({ event: RequestEvent<Record<string, string>, string | null>event, resolve: (event: RequestEvent, opts?: ResolveOptions) => Promise<Response>resolve }) => {
var console: ConsoleThe console module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:
- A
Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
- A global
console instance configured to write to process.stdout and
process.stderr. The global console can be used without importing the node:console module.
Warning: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the note on process I/O for
more information.
Example using the global console:
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
// Error: Whoops, something bad happened
// at [eval]:5:15
// at Script.runInThisContext (node:vm:132:18)
// at Object.runInThisContext (node:vm:309:38)
// at node:internal/process/execution:77:19
// at [eval]-wrapper:6:22
// at evalScript (node:internal/process/execution:76:60)
// at node:internal/main/eval_string:23:3
const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
Example using the Console class:
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);
myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err
const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
console.Console.log(message?: any, ...optionalParams: any[]): void (+1 overload)Prints to stdout with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to printf(3)
(the arguments are all passed to util.format()).
const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
See util.format() for more information.
log('second pre-processing');
const const result: Responseresult = await resolve: (event: RequestEvent, opts?: ResolveOptions) => Promise<Response>resolve(event: RequestEvent<Record<string, string>, string | null>event, {
ResolveOptions.transformPageChunk?: ((input: {
html: string;
done: boolean;
}) => MaybePromise<string | undefined>) | undefined
Applies custom transforms to HTML. If done is true, it's the final chunk. Chunks are not guaranteed to be well-formed HTML
(they could include an element's opening tag but not its closing tag, for example)
but they will always be split at sensible boundaries such as %sveltekit.head% or layout/page components.
transformPageChunk: ({ html: stringhtml }) => {
var console: ConsoleThe console module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:
- A
Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
- A global
console instance configured to write to process.stdout and
process.stderr. The global console can be used without importing the node:console module.
Warning: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the note on process I/O for
more information.
Example using the global console:
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
// Error: Whoops, something bad happened
// at [eval]:5:15
// at Script.runInThisContext (node:vm:132:18)
// at Object.runInThisContext (node:vm:309:38)
// at node:internal/process/execution:77:19
// at [eval]-wrapper:6:22
// at evalScript (node:internal/process/execution:76:60)
// at node:internal/main/eval_string:23:3
const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
Example using the Console class:
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);
myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err
const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
console.Console.log(message?: any, ...optionalParams: any[]): void (+1 overload)Prints to stdout with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to printf(3)
(the arguments are all passed to util.format()).
const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
See util.format() for more information.
log('second transform');
return html: stringhtml;
},
ResolveOptions.preload?: ((input: {
type: "font" | "css" | "js" | "asset";
path: string;
}) => boolean) | undefined
Determines which files should be preloaded. Files are preloaded via <link> tags added to the
<head> tag; if output.linkHeaderPreload is enabled, dynamically rendered pages use the
Link response header instead.
By default, js and css files will be preloaded.
preload: () => {
var console: ConsoleThe console module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:
- A
Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
- A global
console instance configured to write to process.stdout and
process.stderr. The global console can be used without importing the node:console module.
Warning: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the note on process I/O for
more information.
Example using the global console:
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
// Error: Whoops, something bad happened
// at [eval]:5:15
// at Script.runInThisContext (node:vm:132:18)
// at Object.runInThisContext (node:vm:309:38)
// at node:internal/process/execution:77:19
// at [eval]-wrapper:6:22
// at evalScript (node:internal/process/execution:76:60)
// at node:internal/main/eval_string:23:3
const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
Example using the Console class:
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);
myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err
const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
console.Console.log(message?: any, ...optionalParams: any[]): void (+1 overload)Prints to stdout with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to printf(3)
(the arguments are all passed to util.format()).
const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
See util.format() for more information.
log('second preload');
return true;
},
ResolveOptions.filterSerializedResponseHeaders?: ((name: string, value: string) => boolean) | undefinedDetermines which headers should be included in serialized responses when a load function loads a resource with fetch.
By default, none will be included.
filterSerializedResponseHeaders: () => {
// this one wins as it's the first defined in the chain
var console: ConsoleThe console module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:
- A
Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
- A global
console instance configured to write to process.stdout and
process.stderr. The global console can be used without importing the node:console module.
Warning: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the note on process I/O for
more information.
Example using the global console:
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
// Error: Whoops, something bad happened
// at [eval]:5:15
// at Script.runInThisContext (node:vm:132:18)
// at Object.runInThisContext (node:vm:309:38)
// at node:internal/process/execution:77:19
// at [eval]-wrapper:6:22
// at evalScript (node:internal/process/execution:76:60)
// at node:internal/main/eval_string:23:3
const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
Example using the Console class:
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);
myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err
const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
console.Console.log(message?: any, ...optionalParams: any[]): void (+1 overload)Prints to stdout with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to printf(3)
(the arguments are all passed to util.format()).
const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
See util.format() for more information.
log('second filterSerializedResponseHeaders');
return true;
}
});
var console: ConsoleThe console module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:
- A
Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
- A global
console instance configured to write to process.stdout and
process.stderr. The global console can be used without importing the node:console module.
Warning: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the note on process I/O for
more information.
Example using the global console:
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
// Error: Whoops, something bad happened
// at [eval]:5:15
// at Script.runInThisContext (node:vm:132:18)
// at Object.runInThisContext (node:vm:309:38)
// at node:internal/process/execution:77:19
// at [eval]-wrapper:6:22
// at evalScript (node:internal/process/execution:76:60)
// at node:internal/main/eval_string:23:3
const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
Example using the Console class:
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);
myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err
const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
console.Console.log(message?: any, ...optionalParams: any[]): void (+1 overload)Prints to stdout with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to printf(3)
(the arguments are all passed to util.format()).
const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
See util.format() for more information.
log('second post-processing');
return const result: Responseresult;
};
export const const handle: Handlehandle = function sequence(...handlers: Handle[]): HandleA helper function for sequencing multiple handle calls in a middleware-like manner.
The behavior for the handle options is as follows:
transformPageChunk is applied in reverse order and merged
preload is applied in forward order, the first option "wins" and no preload options after it are called
filterSerializedResponseHeaders behaves the same as preload
src/hooks.serverimport { sequence } from '@sveltejs/kit/hooks';
/// type: import('@sveltejs/kit/hooks').Handle
async function first({ event, resolve }) {
console.log('first pre-processing');
const result = await resolve(event, {
transformPageChunk: ({ html }) => {
// transforms are applied in reverse order
console.log('first transform');
return html;
},
preload: () => {
// this one wins as it's the first defined in the chain
console.log('first preload');
return true;
}
});
console.log('first post-processing');
return result;
}
/// type: import('@sveltejs/kit/hooks').Handle
async function second({ event, resolve }) {
console.log('second pre-processing');
const result = await resolve(event, {
transformPageChunk: ({ html }) => {
console.log('second transform');
return html;
},
preload: () => {
console.log('second preload');
return true;
},
filterSerializedResponseHeaders: () => {
// this one wins as it's the first defined in the chain
console.log('second filterSerializedResponseHeaders');
return true;
}
});
console.log('second post-processing');
return result;
}
export const handle = sequence(first, second);
The example above would print:
first pre-processing
first preload
second pre-processing
second filterSerializedResponseHeaders
second transform
first transform
second post-processing
first post-processing
Calling resolve invokes the next handler in the sequence (or SvelteKit itself, if it is the last one). To pass data between handlers, use event.locals.
sequence(const first: Handlefirst, const second: Handlesecond);The example above would print:
first pre-processing
first preload
second pre-processing
second filterSerializedResponseHeaders
second transform
first transform
second post-processing
first post-processingCalling resolve invokes the next handler in the sequence (or SvelteKit itself, if it is the last one). To pass data between handlers, use event.locals.
function sequence(...handlers: Handle[]): Handle;CaughtError
The error passed to the handleError hooks.
Use the kind discriminant to distinguish errors from your app (thrown with the
error helper), errors generated by
SvelteKit itself (such as 404s), validation errors, and unknown errors (thrown by your code,
or code it calls).
type CaughtError<
Issue extends StandardSchemaV1.Issue =
StandardSchemaV1.Issue
> =
| {
[Kind in keyof CaughtErrorMap]: {
/** Identifies the category and origin of the error */
kind: Kind;
/** The caught error. Its type depends on `kind` */
error: CaughtErrorMap[Kind];
/** Only present for validation errors */
issues?: undefined;
};
}[keyof CaughtErrorMap]
| ValidationCaughtError<Issue>;ClientCaughtError
The error passed to the client-side handleError hook.
type ClientCaughtError = Exclude<
CaughtError,
{ kind: 'validation' }
>;ClientInit
Available since 2.10.0
The init will be invoked once the app starts in the browser
type ClientInit = () => MaybePromise<void>;Handle
The handle hook runs every time the SvelteKit server receives a request and
determines the response.
It receives an event object representing the request and a function called resolve, which renders the route and generates a Response.
This allows you to modify response headers or bodies, or bypass SvelteKit entirely (for implementing routes programmatically, for example).
type Handle = (input: {
event: RequestEvent;
resolve: (
event: RequestEvent,
opts?: ResolveOptions
) => Promise<Response>;
}) => MaybePromise<Response>;HandleClientError
The client-side handleError hook runs for every error thrown while navigating, except redirects.
Errors that were already transformed by the server-side hook are not passed to it a second time.
The kind property discriminates between app errors (thrown with the error helper),
framework errors (generated by SvelteKit itself, such as 404s) and unknown errors (thrown by your code, or code it calls).
The hook returns an object matching App.Error, in which status and message are optional — return them only to
override the defaults. Omitted properties are inherited from the caught error: the body passed to error(...) for app errors,
the status and safe message for framework errors, and 500 / 'Internal Error' for unknown errors. Return nothing to
keep the defaults entirely (if you augment App.Error with required properties, you must return those).
Make sure that this function never throws an error.
type HandleClientError = (
input: ClientCaughtError & { event: NavigationEvent }
) => MaybePromise<
| AppErrorWithOptionalDefaults
| VoidIfNoRequiredAppErrorProperties
>;HandleFetch
The handleFetch hook allows you to modify (or replace) the result of an event.fetch call that runs on the server (or during prerendering) inside an endpoint, load, action, handle, handleError or reroute.
type HandleFetch = (input: {
event: RequestEvent;
request: Request;
fetch: typeof fetch;
}) => MaybePromise<Response>;HandleServerError
The server-side handleError hook runs for every error thrown while responding to a request, except redirects.
The kind property discriminates between app errors (thrown with the error helper),
framework errors (generated by SvelteKit itself, such as 404s), validation errors (caused by invalid remote function arguments)
and unknown errors (thrown by your code, or code it calls).
The hook returns an object matching App.Error, in which status and message are optional — return them only to
override the defaults. Omitted properties are inherited from the caught error: the body passed to error(...) for app errors,
the status and safe message for framework and validation errors, and 500 / 'Internal Error' for unknown errors. Return nothing to
keep the defaults entirely (if you augment App.Error with required properties, you must return those).
Make sure that this function never throws an error.
type HandleServerError<
Issue extends StandardSchemaV1.Issue =
StandardSchemaV1.Issue
> = (
input: CaughtError<Issue> & { event: RequestEvent }
) => MaybePromise<
| AppErrorWithOptionalDefaults
| VoidIfNoRequiredAppErrorProperties
>;Reroute
Available since 2.3.0
The reroute hook allows you to modify the URL before it is used to determine which route to render.
type Reroute = (event: {
url: URL;
fetch: typeof fetch;
}) => MaybePromise<void | string>;ResolveOptions
interface ResolveOptions {…}transformPageChunk?: (input: { html: string; done: boolean }) => MaybePromise<string | undefined>;inputthe html chunk and the info if this is the last chunk
Applies custom transforms to HTML. If done is true, it's the final chunk. Chunks are not guaranteed to be well-formed HTML
(they could include an element's opening tag but not its closing tag, for example)
but they will always be split at sensible boundaries such as %sveltekit.head% or layout/page components.
filterSerializedResponseHeaders?: (name: string, value: string) => boolean;nameheader namevalueheader value
Determines which headers should be included in serialized responses when a load function loads a resource with fetch.
By default, none will be included.
preload?: (input: { type: 'font' | 'css' | 'js' | 'asset'; path: string }) => boolean;inputthe type of the file and its path
Determines which files should be preloaded. Files are preloaded via <link> tags added to the
<head> tag; if output.linkHeaderPreload is enabled, dynamically rendered pages use the
Link response header instead.
By default, js and css files will be preloaded.
ServerInit
Available since 2.10.0
The init will be invoked before the server responds to its first request
type ServerInit = () => MaybePromise<void>;Transport
Available since 2.11.0
The transport hook allows you to transport custom types across the server/client boundary.
Each transporter has a pair of encode and decode functions. On the server, encode determines whether a value is an instance of the custom type and, if so, returns a non-falsy encoding of the value which can be an object or an array (or false otherwise).
In the browser, decode turns the encoding back into an instance of the custom type.
import type { type Transport = {
[x: string]: Transporter<any, any>;
}
The transport hook allows you to transport custom types across the server/client boundary.
Each transporter has a pair of encode and decode functions. On the server, encode determines whether a value is an instance of the custom type and, if so, returns a non-falsy encoding of the value which can be an object or an array (or false otherwise).
In the browser, decode turns the encoding back into an instance of the custom type.
import type { Transport } from '@sveltejs/kit/hooks';
declare class MyCustomType {
data: any
}
// hooks.js
export const transport: Transport = {
MyCustomType: {
encode: (value) => value instanceof MyCustomType && [value.data],
decode: ([data]) => new MyCustomType(data)
}
};
Transport } from '@sveltejs/kit/hooks';
declare class class MyCustomTypeMyCustomType {
MyCustomType.data: anydata: any
}
// hooks.js
export const const transport: Transporttransport: type Transport = {
[x: string]: Transporter<any, any>;
}
The transport hook allows you to transport custom types across the server/client boundary.
Each transporter has a pair of encode and decode functions. On the server, encode determines whether a value is an instance of the custom type and, if so, returns a non-falsy encoding of the value which can be an object or an array (or false otherwise).
In the browser, decode turns the encoding back into an instance of the custom type.
import type { Transport } from '@sveltejs/kit/hooks';
declare class MyCustomType {
data: any
}
// hooks.js
export const transport: Transport = {
MyCustomType: {
encode: (value) => value instanceof MyCustomType && [value.data],
decode: ([data]) => new MyCustomType(data)
}
};
Transport = {
type MyCustomType: {
encode: (value: any) => false | any[];
decode: ([data]: any) => MyCustomType;
}
MyCustomType: {
Transporter<any, any>.encode: (value: any) => anyencode: (value: anyvalue) => value: anyvalue instanceof class MyCustomTypeMyCustomType && [value: MyCustomTypevalue.MyCustomType.data: anydata],
Transporter<any, any>.decode: (data: any) => anydecode: ([data: anydata]) => new constructor MyCustomType(): MyCustomTypeMyCustomType(data: anydata)
}
};type Transport = Record<string, Transporter>;Transporter
A member of the transport hook.
interface Transporter<
T = any,
U =
any /* minus falsy values, but we can't properly express that */
> {…}encode: (value: T) => false | U;decode: (data: U) => T;Edit this page on GitHub llms.txt