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SvelteKit入门

Web 标准

在整个文档中，您将看到对 SvelteKit 构建在其之上的标准 Web API 的引用。我们并没有重新发明轮子，而是使用平台，这意味着您现有的 Web 开发技能适用于 SvelteKit。反过来，花时间学习 SvelteKit 将帮助您成为其他地方更好的 Web 开发人员。

这些 API 在所有现代浏览器以及许多非浏览器环境（如 Cloudflare Workers、Deno 和 Vercel Functions）中可用。在开发过程中，以及在针对基于 Node 的环境（包括 AWS Lambda）的 适配器 中，它们在必要时通过 polyfill 提供（目前是这样——Node 正在快速添加对更多 Web 标准的支持）。

特别是，您将熟悉以下内容

Fetch API

SvelteKit 使用 fetch 从网络获取数据。它在 钩子 和 服务器路由 以及浏览器中可用。

在 load 函数、服务器钩子 和 API 路由 中可以使用 fetch 的特殊版本，用于在服务器端渲染期间直接调用端点，而无需进行 HTTP 调用，同时保留凭据。（要在 load 之外的服务器端代码中进行凭据化获取，您必须显式传递 cookie 和/或 authorization 标头。）它还允许您发出相对请求，而服务器端 fetch 通常需要一个完全限定的 URL。

除了 fetch 本身之外，Fetch API 还包括以下接口

Request

在 钩子 和 服务器路由 中可以通过 event.request 访问 Request 的实例。它包含诸如 request.json() 和 request.formData() 之类的有用方法，用于获取发布到端点的的数据。

Response

从 await fetch(...) 和 +server.js 文件中的处理程序返回 Response 的实例。从根本上说，SvelteKit 应用是一个将 Request 转换为 Response 的机器。

Headers

Headers 接口允许您读取传入的 request.headers 并设置传出的 response.headers。例如，您可以获取如下所示的 request.headers，并使用 json 便利函数 发送修改后的 response.headers

src/routes/what-is-my-user-agent/+server
import { function json(data: any, init?: ResponseInit | undefined): Response
Create a JSON Response object from the supplied data.


@paramdata The value that will be serialized as JSON.
@paraminit Options such as status and headers that will be added to the response. Content-Type: application/json and Content-Length headers will be added automatically.
json } from '@sveltejs/kit';

/** @type {import('./$types').RequestHandler} */
export function 
function GET({ request }: {
    request: any;
}): Response
@type{import('./$types').RequestHandler}
GET({ request: anyrequest }) {
	// log all headers
	var console: Console
The 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 calling require('console').
    • 



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
@seesource
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.


@sincev0.1.100
log(...request: anyrequest.headers);

	// create a JSON Response using a header we received
	return function json(data: any, init?: ResponseInit | undefined): Response
Create a JSON Response object from the supplied data.


@paramdata The value that will be serialized as JSON.
@paraminit Options such as status and headers that will be added to the response. Content-Type: application/json and Content-Length headers will be added automatically.
json({
		// retrieve a specific header
		userAgent: anyuserAgent: request: anyrequest.headers.get('user-agent')
	}, {
		// set a header on the response
		ResponseInit.headers?: HeadersInit | undefinedheaders: { 'x-custom-header': 'potato' }
	});
}
import { function json(data: any, init?: ResponseInit | undefined): Response
Create a JSON Response object from the supplied data.


@paramdata The value that will be serialized as JSON.
@paraminit Options such as status and headers that will be added to the response. Content-Type: application/json and Content-Length headers will be added automatically.
json } from '@sveltejs/kit';
import type { 
type RequestHandler = (event: Kit.RequestEvent<Record<string, any>, string | null>) => MaybePromise<Response>
type RequestHandler = (event: Kit.RequestEvent<Record<string, any>, string | null>) => MaybePromise<Response>
RequestHandler } from './$types';

export const const GET: RequestHandlerGET: 
type RequestHandler = (event: Kit.RequestEvent<Record<string, any>, string | null>) => MaybePromise<Response>
type RequestHandler = (event: Kit.RequestEvent<Record<string, any>, string | null>) => MaybePromise<Response>
RequestHandler = ({ request: Request
The original request object


request }) => {
	// log all headers
	var console: Console
The 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 calling require('console').
    • 



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
@seesource
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.


@sincev0.1.100
log(...request: Request
The original request object


request.Request.headers: Headers
Returns a Headers object consisting of the headers associated with request. Note that headers added in the network layer by the user agent will not be accounted for in this object, e.g., the “Host” header.


MDN Reference


headers);

	// create a JSON Response using a header we received
	return function json(data: any, init?: ResponseInit | undefined): Response
Create a JSON Response object from the supplied data.


@paramdata The value that will be serialized as JSON.
@paraminit Options such as status and headers that will be added to the response. Content-Type: application/json and Content-Length headers will be added automatically.
json({
		// retrieve a specific header
		userAgent: string | nulluserAgent: request: Request
The original request object


request.Request.headers: Headers
Returns a Headers object consisting of the headers associated with request. Note that headers added in the network layer by the user agent will not be accounted for in this object, e.g., the “Host” header.


MDN Reference


headers.Headers.get(name: string): string | null
MDN Reference


get('user-agent')
	}, {
		// set a header on the response
		ResponseInit.headers?: HeadersInit | undefinedheaders: { 'x-custom-header': 'potato' }
	});
};

FormData

在处理 HTML 原生表单提交时，您将使用 FormData 对象。

src/routes/hello/+server
import { function json(data: any, init?: ResponseInit | undefined): Response
Create a JSON Response object from the supplied data.


@paramdata The value that will be serialized as JSON.
@paraminit Options such as status and headers that will be added to the response. Content-Type: application/json and Content-Length headers will be added automatically.
json } from '@sveltejs/kit';

/** @type {import('./$types').RequestHandler} */
export async function function POST(event: any): Promise<Response>
@type{import('./$types').RequestHandler}
POST(event: anyevent) {
	const const body: anybody = await event: anyevent.request.formData();

	// log all fields
	var console: Console
The 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 calling require('console').
    • 



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
@seesource
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.


@sincev0.1.100
log([...const body: anybody]);

	return function json(data: any, init?: ResponseInit | undefined): Response
Create a JSON Response object from the supplied data.


@paramdata The value that will be serialized as JSON.
@paraminit Options such as status and headers that will be added to the response. Content-Type: application/json and Content-Length headers will be added automatically.
json({
		// get a specific field's value
		name: anyname: const body: anybody.get('name') ?? 'world'
	});
}
import { function json(data: any, init?: ResponseInit | undefined): Response
Create a JSON Response object from the supplied data.


@paramdata The value that will be serialized as JSON.
@paraminit Options such as status and headers that will be added to the response. Content-Type: application/json and Content-Length headers will be added automatically.
json } from '@sveltejs/kit';
import type { 
type RequestHandler = (event: Kit.RequestEvent<Record<string, any>, string | null>) => MaybePromise<Response>
type RequestHandler = (event: Kit.RequestEvent<Record<string, any>, string | null>) => MaybePromise<Response>
RequestHandler } from './$types';

export const const POST: RequestHandlerPOST: 
type RequestHandler = (event: Kit.RequestEvent<Record<string, any>, string | null>) => MaybePromise<Response>
type RequestHandler = (event: Kit.RequestEvent<Record<string, any>, string | null>) => MaybePromise<Response>
RequestHandler = async (event: Kit.RequestEvent<Record<string, any>, string | null>event) => {
	const const body: FormDatabody = await event: Kit.RequestEvent<Record<string, any>, string | null>event.RequestEvent<Record<string, any>, string | null>.request: Request
The original request object


request.Body.formData(): Promise<FormData>
MDN Reference


formData();

	// log all fields
	var console: Console
The 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 calling require('console').
    • 



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
@seesource
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.


@sincev0.1.100
log([...const body: FormDatabody]);

	return function json(data: any, init?: ResponseInit | undefined): Response
Create a JSON Response object from the supplied data.


@paramdata The value that will be serialized as JSON.
@paraminit Options such as status and headers that will be added to the response. Content-Type: application/json and Content-Length headers will be added automatically.
json({
		// get a specific field's value
		name: FormDataEntryValuename: const body: FormDatabody.FormData.get(name: string): FormDataEntryValue | null
MDN Reference


get('name') ?? 'world'
	});
};

Stream API

大多数情况下，您的端点将返回完整的数据，如上面的 userAgent 示例所示。有时，您可能需要返回一个响应，该响应太大而无法一次性放入内存，或者以块的形式传递，为此平台提供了 流——ReadableStream、WritableStream 和 TransformStream。

URL API

URL 由 URL 接口表示，该接口包含诸如 origin 和 pathname（以及在浏览器中，hash）之类的有用属性。此接口出现在各个地方——钩子 和 服务器路由 中的 event.url，$page.url 在 页面 中，beforeNavigate 和 afterNavigate 中的 from 和 to 等等。

URLSearchParams

在您遇到 URL 的任何地方，您都可以通过 url.searchParams 访问查询参数，它是一个 URLSearchParams 的实例。

const const foo: string | nullfoo = const url: URLurl.URL.searchParams: URLSearchParams
MDN Reference


searchParams.URLSearchParams.get(name: string): string | null
Returns the first value associated to the given search parameter.


MDN Reference


get('foo');

Web Crypto

可以通过全局 crypto 提供 Web Crypto API。它在内部用于 内容安全策略 标头，但您也可以将其用于生成 UUID 等操作。

const const uuid: `${string}-${string}-${string}-${string}-${string}`uuid = var crypto: Crypto
MDN Reference


crypto.Crypto.randomUUID(): `${string}-${string}-${string}-${string}-${string}`
Available only in secure contexts.


MDN Reference


randomUUID();

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