@achingbrain/node-fetch 中文文档教程

发布于 3年前 浏览 20 项目主页 更新于 3年前

Temporary fork ????

这是 node-fetch 的临时分支,合并了来自 node-fetch#1172 的修复。 它不会被更新或维护。

node-fetch

npm 版本构建状态覆盖状态安装尺寸Discord

window.fetch 引入 Node.js 的轻量级模块

(我们正在寻找 v2 维护者和合作者)

Backers

Motivation

而不是在 Node.js 中实现 XMLHttpRequest 以运行特定于浏览器的 Fetch polyfill,为什么不直接从原生 httpfetch API? 因此,node-fetch 是 Node.js 运行时上 window.fetch 兼容 API 的最小代码。

请参阅 Matt Andrews 的 isomorphic-fetch 或 Leonardo Quixada 的 cross-fetch 用于同构使用(为服务器端导出 node-fetch,为客户端导出 whatwg-fetch)。

Features

  • Stay consistent with window.fetch API.
  • Make conscious trade-off when following WHATWG fetch spec and stream spec implementation details, document known differences.
  • Use native promise but allow substituting it with [insert your favorite promise library].
  • Use native Node streams for body on both request and response.
  • Decode content encoding (gzip/deflate) properly and convert string output (such as res.text() and res.json()) to UTF-8 automatically.
  • Useful extensions such as timeout, redirect limit, response size limit, explicit errors for troubleshooting.

Difference from client-side fetch

  • See Known Differences for details.
  • If you happen to use a missing feature that window.fetch offers, feel free to open an issue.
  • Pull requests are welcomed too!

Installation

当前稳定版本 (2.x)

$ npm install node-fetch

Loading and configuring the module

我们建议您通过 require 加载模块,直到 ES 模块在 node 中稳定:

const fetch = require('node-fetch');

如果您使用的是原生以外的 Promise 库,通过 fetch.Promise 设置它:

const Bluebird = require('bluebird');

fetch.Promise = Bluebird;

Common Usage

注意:下面的文档是最新的 2.x 版本; 请参阅 1.x 自述文件更新日志2.x 升级差异指南

Plain text or HTML

fetch('https://github.com/')
    .then(res => res.text())
    .then(body => console.log(body));

JSON

fetch('https://api.github.com/users/github')
    .then(res => res.json())
    .then(json => console.log(json));

Simple Post

fetch('https://httpbin.org/post', { method: 'POST', body: 'a=1' })
    .then(res => res.json()) // expecting a json response
    .then(json => console.log(json));

Post with JSON

const body = { a: 1 };

fetch('https://httpbin.org/post', {
        method: 'post',
        body:    JSON.stringify(body),
        headers: { 'Content-Type': 'application/json' },
    })
    .then(res => res.json())
    .then(json => console.log(json));

Post with form parameters

从 v7.5.0 开始,URLSearchParams 在 Node.js 中可用。 更多使用方法见官方文档

注意:Content-Type 标头仅在 URLSearchParams 实例给出时自动设置为 x-www-form-urlencoded

const { URLSearchParams } = require('url');

const params = new URLSearchParams();
params.append('a', 1);

fetch('https://httpbin.org/post', { method: 'POST', body: params })
    .then(res => res.json())
    .then(json => console.log(json));

Handling exceptions

注意:3xx-5xx 响应是NOT 异常,应该在then() 中处理; 有关详细信息,请参阅下一节。

在 fetch promise 链中添加一个 catch 将捕获 所有 异常,例如来自节点核心库的错误、网络错误和操作错误,这些都是 FetchError 的实例。 有关详细信息,请参阅错误处理文档

fetch('https://domain.invalid/')
    .catch(err => console.error(err));

Handling client and server errors

通常创建一个辅助函数来检查响应是否不包含客户端 (4xx) 或服务器 (5xx) 错误响应:

function checkStatus(res) {
    if (res.ok) { // res.status >= 200 && res.status < 300
        return res;
    } else {
        throw MyCustomError(res.statusText);
    }
}

fetch('https://httpbin.org/status/400')
    .then(checkStatus)
    .then(res => console.log('will not get here...'))

Advanced Usage

Streams

“Node.js 方式”是尽可能使用流:

fetch('https://assets-cdn.github.com/images/modules/logos_page/Octocat.png')
    .then(res => {
        const dest = fs.createWriteStream('./octocat.png');
        res.body.pipe(dest);
    });

在 Node.js 14 中,您还可以使用读取 body 的异步迭代器; 但是,要小心抓住 错误——响应运行的时间越长,遇到错误的可能性就越大。

const fetch = require('node-fetch');
const response = await fetch('https://httpbin.org/stream/3');
try {
    for await (const chunk of response.body) {
        console.dir(JSON.parse(chunk.toString()));
    }
} catch (err) {
    console.error(err.stack);
}

在 Node.js 12 中,您还可以使用异步迭代器来读取 body; 然而,带有流的异步迭代器 直到 Node.js 14 才成熟,所以你需要做一些额外的工作来确保你处理错误 直接从流中等待它响应完全关闭。

const fetch = require('node-fetch');
const read = async body => {
    let error;
    body.on('error', err => {
        error = err;
    });
    for await (const chunk of body) {
        console.dir(JSON.parse(chunk.toString()));
    }
    return new Promise((resolve, reject) => {
        body.on('close', () => {
            error ? reject(error) : resolve();
        });
    });
};
try {
    const response = await fetch('https://httpbin.org/stream/3');
    await read(response.body);
} catch (err) {
    console.error(err.stack);
}

Buffer

如果您更喜欢完整缓存二进制数据,请使用 buffer()。 (注意:buffer() 是一个 node-fetch-only API)

const fileType = require('file-type');

fetch('https://assets-cdn.github.com/images/modules/logos_page/Octocat.png')
    .then(res => res.buffer())
    .then(buffer => fileType(buffer))
    .then(type => { /* ... */ });

Accessing Headers and other Meta data

fetch('https://github.com/')
    .then(res => {
        console.log(res.ok);
        console.log(res.status);
        console.log(res.statusText);
        console.log(res.headers.raw());
        console.log(res.headers.get('content-type'));
    });

Extract Set-Cookie Header

与浏览器不同,您可以使用 Set-Cookie 手动访问原始标头 <代码>标题.raw()。 这是一个仅限 node-fetch 的 API。

fetch(url).then(res => {
    // returns an array of values, instead of a string of comma-separated values
    console.log(res.headers.raw()['set-cookie']);
});

Post data using a file stream

const { createReadStream } = require('fs');

const stream = createReadStream('input.txt');

fetch('https://httpbin.org/post', { method: 'POST', body: stream })
    .then(res => res.json())
    .then(json => console.log(json));

Post with form-data (detect multipart)

const FormData = require('form-data');

const form = new FormData();
form.append('a', 1);

fetch('https://httpbin.org/post', { method: 'POST', body: form })
    .then(res => res.json())
    .then(json => console.log(json));

// OR, using custom headers
// NOTE: getHeaders() is non-standard API

const form = new FormData();
form.append('a', 1);

const options = {
    method: 'POST',
    body: form,
    headers: form.getHeaders()
}

fetch('https://httpbin.org/post', options)
    .then(res => res.json())
    .then(json => console.log(json));

Request cancellation with AbortSignal

注意:您只能在 Node >= v8.0.0 上取消流请求

您可以使用 AbortController 取消请求。 建议的实施方式是 abort-controller

请求在 150 毫秒后超时的示例如下所示:

import AbortController from 'abort-controller';

const controller = new AbortController();
const timeout = setTimeout(
  () => { controller.abort(); },
  150,
);

fetch(url, { signal: controller.signal })
  .then(res => res.json())
  .then(
    data => {
      useData(data)
    },
    err => {
      if (err.name === 'AbortError') {
        // request was aborted
      }
    },
  )
  .finally(() => {
    clearTimeout(timeout);
  });

参见 测试用例< /a> 更多示例。

API

fetch(url[, options])

  • url A string representing the URL for fetching
  • options Options for the HTTP(S) request
  • Returns: Promise&lt;[Response](#class-response)&gt;

执行 HTTP(S) 提取。

url应该是一个绝对的url,比如https://example.com/。 将产生路径相对 URL (/file/under/root) 或协议相对 URL (//can-be-http-or-https.com/)在被拒绝的 Promise 中。

Options

默认值显示在每个选项键之后。

{
    // These properties are part of the Fetch Standard
    method: 'GET',
    headers: {},        // request headers. format is the identical to that accepted by the Headers constructor (see below)
    body: null,         // request body. can be null, a string, a Buffer, a Blob, or a Node.js Readable stream
    redirect: 'follow', // set to `manual` to extract redirect headers, `error` to reject redirect
    signal: null,       // pass an instance of AbortSignal to optionally abort requests

    // The following properties are node-fetch extensions
    follow: 20,         // maximum redirect count. 0 to not follow redirect
    timeout: 0,         // req/res timeout in ms, it resets on redirect. 0 to disable (OS limit applies). Signal is recommended instead.
    compress: true,     // support gzip/deflate content encoding. false to disable
    size: 0,            // maximum response body size in bytes. 0 to disable
    agent: null         // http(s).Agent instance or function that returns an instance (see below)
}
Default Headers

如果没有设置任何值,将自动发送以下请求头:

HeaderValue
Accept-Encodinggzip,deflate (when options.compress === true)
Accept*/*
Connectionclose (when no options.agent is present)
Content-Length(automatically calculated, if possible)
Transfer-Encodingchunked (when req.body is a stream)
User-Agentnode-fetch/1.0 (+https://github.com/bitinn/node-fetch)

注意:当body 是一个Stream 时,Content-Length 没有设置自动地。

Custom Agent

agent 选项允许您指定超出 Fetch 范围的网络相关选项,包括但不限于以下内容:

  • Support self-signed certificate
  • Use only IPv4 or IPv6
  • Custom DNS Lookup

参见 http.Agent 了解更多信息。

此外,agent 选项接受返回 http(s).Agent 给定当前 URL,这在跨 HTTP 和 HTTPS 协议的重定向链中很有用。

const httpAgent = new http.Agent({
    keepAlive: true
});
const httpsAgent = new https.Agent({
    keepAlive: true
});

const options = {
    agent: function (_parsedURL) {
        if (_parsedURL.protocol == 'http:') {
            return httpAgent;
        } else {
            return httpsAgent;
        }
    }
}

Class: Request

包含有关 URL、方法、标头和正文的信息的 HTTP(S) 请求。 这个类实现了Body 接口。

由于 Node.js 的性质,目前未实现以下属性:

  • type
  • destination
  • referrer
  • referrerPolicy
  • mode
  • credentials
  • cache
  • integrity
  • keepalive

提供了以下节点提取扩展属性:

  • follow
  • compress
  • counter
  • agent

请参阅 options 以了解其确切含义这些扩展。

new Request(input[, options])

(spec-compliant)

  • input A string representing a URL, or another Request (which will be cloned)
  • options [Options][#fetch-options] for the HTTP(S) request

构造一个新的 Request 对象。 构造函数与浏览器中的构造函数相同。

在大多数情况下,直接 fetch(url, options) 比创建一个 Request 对象更简单。

Class: Response

HTTP(S) 响应。 这个类实现了Body 接口。

以下属性目前未在 node-fetch 中实现:

  • Response.error()
  • Response.redirect()
  • type
  • trailer

new Response([body[, options]])

(spec-compliant)

构造一个新的 Response 对象。 构造函数与浏览器中的构造函数相同。

因为 Node.js 不实现服务工作者(此类是为其设计的),所以很少需要直接构造 Response

response.ok

(spec-compliant)

表示请求是否正常结束的便利属性。 如果响应状态大于或等于 200 但小于 300,则计算结果为真。

response.redirected

(spec-compliant)

表示请求是否至少被重定向的便利属性一次。 如果内部重定向计数器大于 0,则计算结果为真。

Class: Headers

此类允许对一组 HTTP 标头进行操作和迭代。 Fetch Standard 中指定的所有方法均已实现。

new Headers([init])

(spec-compliant)

  • init Optional argument to pre-fill the Headers object

构造一个新的 Headers 对象。 init 可以是 nullHeaders 对象、键值映射对象或任何可迭代对象。

// Example adapted from https://fetch.spec.whatwg.org/#example-headers-class

const meta = {
  'Content-Type': 'text/xml',
  'Breaking-Bad': '<3'
};
const headers = new Headers(meta);

// The above is equivalent to
const meta = [
  [ 'Content-Type', 'text/xml' ],
  [ 'Breaking-Bad', '<3' ]
];
const headers = new Headers(meta);

// You can in fact use any iterable objects, like a Map or even another Headers
const meta = new Map();
meta.set('Content-Type', 'text/xml');
meta.set('Breaking-Bad', '<3');
const headers = new Headers(meta);
const copyOfHeaders = new Headers(headers);

Interface: Body

Body 是一个抽象接口,其方法适用于 RequestResponse类。

目前node-fetch中还没有实现以下方法:

  • formData()

body.body

(deviation from spec)

数据封装在Body对象中。 请注意,虽然 Fetch Standard 要求属性始终是 WHATWG ReadableStream,但在 node-fetch 中它是一个 Node.js Readable

body.bodyUsed

(spec-compliant)

  • Boolean

一个布尔属性,表示这个身体是否已经被消耗。 根据规格,消耗的身体不能再次使用。

body.arrayBuffer()

body.blob()

body.json()

body.text()

(spec-compliant)

  • Returns: Promise

使用正文并返回将解析为其中一种格式的承诺。

body.buffer()

(node-fetch extension)

  • Returns: Promise&lt;Buffer&gt;

使用正文并返回将解析为 Buffer 的承诺。

body.textConverted()

(node-fetch extension)

  • Returns: Promise&lt;String&gt;

body.text() 相同,只是不总是转换为 UTF-8,而是执行编码嗅探如果可能,将文本转换为 UTF-8。

(此 API 需要 npm 包 encoding 的可选依赖项,您需要手动安装。webpack 用户可能会看到 警告消息 由于此可选依赖项。)

Class: FetchError

(node-fetch extension)

抓取过程中的操作错误。 有关详细信息,请参阅 ERROR-HANDLING.md

Class: AbortError

(node-fetch extension)

当响应 AbortSignal 中止请求时抛出的错误abort 事件。 它具有 AbortErrorname 属性。 有关详细信息,请参阅 ERROR-HANDLING.MD

Acknowledgement

感谢 github/fetch 提供可靠的实现参考。

node-fetch v1 由 @bitinn 维护; v2 由 @TimothyGu@bitinn@jimmywarting; v2 自述文件由 @jkantr 编写。

License

麻省理工学院

[mdn-headers]:https://developer.mozilla.org/en-US/docs/Web/API/Headers

???? Temporary fork ????

This is a temporary fork of node-fetch with the fix from node-fetch#1172 merged. It will not be updated or maintained.

node-fetch

npm versionbuild statuscoverage statusinstall sizeDiscord

A light-weight module that brings window.fetch to Node.js

(We are looking for v2 maintainers and collaborators)

Backers

Motivation

Instead of implementing XMLHttpRequest in Node.js to run browser-specific Fetch polyfill, why not go from native http to fetch API directly? Hence, node-fetch, minimal code for a window.fetch compatible API on Node.js runtime.

See Matt Andrews' isomorphic-fetch or Leonardo Quixada's cross-fetch for isomorphic usage (exports node-fetch for server-side, whatwg-fetch for client-side).

Features

  • Stay consistent with window.fetch API.
  • Make conscious trade-off when following WHATWG fetch spec and stream spec implementation details, document known differences.
  • Use native promise but allow substituting it with [insert your favorite promise library].
  • Use native Node streams for body on both request and response.
  • Decode content encoding (gzip/deflate) properly and convert string output (such as res.text() and res.json()) to UTF-8 automatically.
  • Useful extensions such as timeout, redirect limit, response size limit, explicit errors for troubleshooting.

Difference from client-side fetch

  • See Known Differences for details.
  • If you happen to use a missing feature that window.fetch offers, feel free to open an issue.
  • Pull requests are welcomed too!

Installation

Current stable release (2.x)

$ npm install node-fetch

Loading and configuring the module

We suggest you load the module via require until the stabilization of ES modules in node:

const fetch = require('node-fetch');

If you are using a Promise library other than native, set it through fetch.Promise:

const Bluebird = require('bluebird');

fetch.Promise = Bluebird;

Common Usage

NOTE: The documentation below is up-to-date with 2.x releases; see the 1.x readme, changelog and 2.x upgrade guide for the differences.

Plain text or HTML

fetch('https://github.com/')
    .then(res => res.text())
    .then(body => console.log(body));

JSON

fetch('https://api.github.com/users/github')
    .then(res => res.json())
    .then(json => console.log(json));

Simple Post

fetch('https://httpbin.org/post', { method: 'POST', body: 'a=1' })
    .then(res => res.json()) // expecting a json response
    .then(json => console.log(json));

Post with JSON

const body = { a: 1 };

fetch('https://httpbin.org/post', {
        method: 'post',
        body:    JSON.stringify(body),
        headers: { 'Content-Type': 'application/json' },
    })
    .then(res => res.json())
    .then(json => console.log(json));

Post with form parameters

URLSearchParams is available in Node.js as of v7.5.0. See official documentation for more usage methods.

NOTE: The Content-Type header is only set automatically to x-www-form-urlencoded when an instance of URLSearchParams is given as such:

const { URLSearchParams } = require('url');

const params = new URLSearchParams();
params.append('a', 1);

fetch('https://httpbin.org/post', { method: 'POST', body: params })
    .then(res => res.json())
    .then(json => console.log(json));

Handling exceptions

NOTE: 3xx-5xx responses are NOT exceptions and should be handled in then(); see the next section for more information.

Adding a catch to the fetch promise chain will catch all exceptions, such as errors originating from node core libraries, network errors and operational errors, which are instances of FetchError. See the error handling document for more details.

fetch('https://domain.invalid/')
    .catch(err => console.error(err));

Handling client and server errors

It is common to create a helper function to check that the response contains no client (4xx) or server (5xx) error responses:

function checkStatus(res) {
    if (res.ok) { // res.status >= 200 && res.status < 300
        return res;
    } else {
        throw MyCustomError(res.statusText);
    }
}

fetch('https://httpbin.org/status/400')
    .then(checkStatus)
    .then(res => console.log('will not get here...'))

Advanced Usage

Streams

The "Node.js way" is to use streams when possible:

fetch('https://assets-cdn.github.com/images/modules/logos_page/Octocat.png')
    .then(res => {
        const dest = fs.createWriteStream('./octocat.png');
        res.body.pipe(dest);
    });

In Node.js 14 you can also use async iterators to read body; however, be careful to catch errors -- the longer a response runs, the more likely it is to encounter an error.

const fetch = require('node-fetch');
const response = await fetch('https://httpbin.org/stream/3');
try {
    for await (const chunk of response.body) {
        console.dir(JSON.parse(chunk.toString()));
    }
} catch (err) {
    console.error(err.stack);
}

In Node.js 12 you can also use async iterators to read body; however, async iterators with streams did not mature until Node.js 14, so you need to do some extra work to ensure you handle errors directly from the stream and wait on it response to fully close.

const fetch = require('node-fetch');
const read = async body => {
    let error;
    body.on('error', err => {
        error = err;
    });
    for await (const chunk of body) {
        console.dir(JSON.parse(chunk.toString()));
    }
    return new Promise((resolve, reject) => {
        body.on('close', () => {
            error ? reject(error) : resolve();
        });
    });
};
try {
    const response = await fetch('https://httpbin.org/stream/3');
    await read(response.body);
} catch (err) {
    console.error(err.stack);
}

Buffer

If you prefer to cache binary data in full, use buffer(). (NOTE: buffer() is a node-fetch-only API)

const fileType = require('file-type');

fetch('https://assets-cdn.github.com/images/modules/logos_page/Octocat.png')
    .then(res => res.buffer())
    .then(buffer => fileType(buffer))
    .then(type => { /* ... */ });

Accessing Headers and other Meta data

fetch('https://github.com/')
    .then(res => {
        console.log(res.ok);
        console.log(res.status);
        console.log(res.statusText);
        console.log(res.headers.raw());
        console.log(res.headers.get('content-type'));
    });

Extract Set-Cookie Header

Unlike browsers, you can access raw Set-Cookie headers manually using Headers.raw(). This is a node-fetch only API.

fetch(url).then(res => {
    // returns an array of values, instead of a string of comma-separated values
    console.log(res.headers.raw()['set-cookie']);
});

Post data using a file stream

const { createReadStream } = require('fs');

const stream = createReadStream('input.txt');

fetch('https://httpbin.org/post', { method: 'POST', body: stream })
    .then(res => res.json())
    .then(json => console.log(json));

Post with form-data (detect multipart)

const FormData = require('form-data');

const form = new FormData();
form.append('a', 1);

fetch('https://httpbin.org/post', { method: 'POST', body: form })
    .then(res => res.json())
    .then(json => console.log(json));

// OR, using custom headers
// NOTE: getHeaders() is non-standard API

const form = new FormData();
form.append('a', 1);

const options = {
    method: 'POST',
    body: form,
    headers: form.getHeaders()
}

fetch('https://httpbin.org/post', options)
    .then(res => res.json())
    .then(json => console.log(json));

Request cancellation with AbortSignal

NOTE: You may cancel streamed requests only on Node >= v8.0.0

You may cancel requests with AbortController. A suggested implementation is abort-controller.

An example of timing out a request after 150ms could be achieved as the following:

import AbortController from 'abort-controller';

const controller = new AbortController();
const timeout = setTimeout(
  () => { controller.abort(); },
  150,
);

fetch(url, { signal: controller.signal })
  .then(res => res.json())
  .then(
    data => {
      useData(data)
    },
    err => {
      if (err.name === 'AbortError') {
        // request was aborted
      }
    },
  )
  .finally(() => {
    clearTimeout(timeout);
  });

See test cases for more examples.

API

fetch(url[, options])

  • url A string representing the URL for fetching
  • options Options for the HTTP(S) request
  • Returns: Promise&lt;[Response](#class-response)&gt;

Perform an HTTP(S) fetch.

url should be an absolute url, such as https://example.com/. A path-relative URL (/file/under/root) or protocol-relative URL (//can-be-http-or-https.com/) will result in a rejected Promise.

Options

The default values are shown after each option key.

{
    // These properties are part of the Fetch Standard
    method: 'GET',
    headers: {},        // request headers. format is the identical to that accepted by the Headers constructor (see below)
    body: null,         // request body. can be null, a string, a Buffer, a Blob, or a Node.js Readable stream
    redirect: 'follow', // set to `manual` to extract redirect headers, `error` to reject redirect
    signal: null,       // pass an instance of AbortSignal to optionally abort requests

    // The following properties are node-fetch extensions
    follow: 20,         // maximum redirect count. 0 to not follow redirect
    timeout: 0,         // req/res timeout in ms, it resets on redirect. 0 to disable (OS limit applies). Signal is recommended instead.
    compress: true,     // support gzip/deflate content encoding. false to disable
    size: 0,            // maximum response body size in bytes. 0 to disable
    agent: null         // http(s).Agent instance or function that returns an instance (see below)
}
Default Headers

If no values are set, the following request headers will be sent automatically:

HeaderValue
Accept-Encodinggzip,deflate (when options.compress === true)
Accept*/*
Connectionclose (when no options.agent is present)
Content-Length(automatically calculated, if possible)
Transfer-Encodingchunked (when req.body is a stream)
User-Agentnode-fetch/1.0 (+https://github.com/bitinn/node-fetch)

Note: when body is a Stream, Content-Length is not set automatically.

Custom Agent

The agent option allows you to specify networking related options which are out of the scope of Fetch, including and not limited to the following:

  • Support self-signed certificate
  • Use only IPv4 or IPv6
  • Custom DNS Lookup

See http.Agent for more information.

In addition, the agent option accepts a function that returns http(s).Agent instance given current URL, this is useful during a redirection chain across HTTP and HTTPS protocol.

const httpAgent = new http.Agent({
    keepAlive: true
});
const httpsAgent = new https.Agent({
    keepAlive: true
});

const options = {
    agent: function (_parsedURL) {
        if (_parsedURL.protocol == 'http:') {
            return httpAgent;
        } else {
            return httpsAgent;
        }
    }
}

Class: Request

An HTTP(S) request containing information about URL, method, headers, and the body. This class implements the Body interface.

Due to the nature of Node.js, the following properties are not implemented at this moment:

  • type
  • destination
  • referrer
  • referrerPolicy
  • mode
  • credentials
  • cache
  • integrity
  • keepalive

The following node-fetch extension properties are provided:

  • follow
  • compress
  • counter
  • agent

See options for exact meaning of these extensions.

new Request(input[, options])

(spec-compliant)

  • input A string representing a URL, or another Request (which will be cloned)
  • options [Options][#fetch-options] for the HTTP(S) request

Constructs a new Request object. The constructor is identical to that in the browser.

In most cases, directly fetch(url, options) is simpler than creating a Request object.

Class: Response

An HTTP(S) response. This class implements the Body interface.

The following properties are not implemented in node-fetch at this moment:

  • Response.error()
  • Response.redirect()
  • type
  • trailer

new Response([body[, options]])

(spec-compliant)

Constructs a new Response object. The constructor is identical to that in the browser.

Because Node.js does not implement service workers (for which this class was designed), one rarely has to construct a Response directly.

response.ok

(spec-compliant)

Convenience property representing if the request ended normally. Will evaluate to true if the response status was greater than or equal to 200 but smaller than 300.

response.redirected

(spec-compliant)

Convenience property representing if the request has been redirected at least once. Will evaluate to true if the internal redirect counter is greater than 0.

Class: Headers

This class allows manipulating and iterating over a set of HTTP headers. All methods specified in the Fetch Standard are implemented.

new Headers([init])

(spec-compliant)

  • init Optional argument to pre-fill the Headers object

Construct a new Headers object. init can be either null, a Headers object, an key-value map object or any iterable object.

// Example adapted from https://fetch.spec.whatwg.org/#example-headers-class

const meta = {
  'Content-Type': 'text/xml',
  'Breaking-Bad': '<3'
};
const headers = new Headers(meta);

// The above is equivalent to
const meta = [
  [ 'Content-Type', 'text/xml' ],
  [ 'Breaking-Bad', '<3' ]
];
const headers = new Headers(meta);

// You can in fact use any iterable objects, like a Map or even another Headers
const meta = new Map();
meta.set('Content-Type', 'text/xml');
meta.set('Breaking-Bad', '<3');
const headers = new Headers(meta);
const copyOfHeaders = new Headers(headers);

Interface: Body

Body is an abstract interface with methods that are applicable to both Request and Response classes.

The following methods are not yet implemented in node-fetch at this moment:

  • formData()

body.body

(deviation from spec)

Data are encapsulated in the Body object. Note that while the Fetch Standard requires the property to always be a WHATWG ReadableStream, in node-fetch it is a Node.js Readable stream.

body.bodyUsed

(spec-compliant)

  • Boolean

A boolean property for if this body has been consumed. Per the specs, a consumed body cannot be used again.

body.arrayBuffer()

body.blob()

body.json()

body.text()

(spec-compliant)

  • Returns: Promise

Consume the body and return a promise that will resolve to one of these formats.

body.buffer()

(node-fetch extension)

  • Returns: Promise&lt;Buffer&gt;

Consume the body and return a promise that will resolve to a Buffer.

body.textConverted()

(node-fetch extension)

  • Returns: Promise&lt;String&gt;

Identical to body.text(), except instead of always converting to UTF-8, encoding sniffing will be performed and text converted to UTF-8 if possible.

(This API requires an optional dependency of the npm package encoding, which you need to install manually. webpack users may see a warning message due to this optional dependency.)

Class: FetchError

(node-fetch extension)

An operational error in the fetching process. See ERROR-HANDLING.md for more info.

Class: AbortError

(node-fetch extension)

An Error thrown when the request is aborted in response to an AbortSignal's abort event. It has a name property of AbortError. See ERROR-HANDLING.MD for more info.

Acknowledgement

Thanks to github/fetch for providing a solid implementation reference.

node-fetch v1 was maintained by @bitinn; v2 was maintained by @TimothyGu, @bitinn and @jimmywarting; v2 readme is written by @jkantr.

License

MIT

[mdn-headers]: https://developer.mozilla.org/en-US/docs/Web/API/Headers

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