@achingbrain/node-fetch 中文文档教程
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
将 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)
- Motivation
- Features
- Difference from client-side fetch
- Installation
- Loading and configuring the module
- Common Usage
- Advanced Usage
- API
- License
- Acknowledgement
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 http
到 fetch
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()
andres.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 和 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);
});
API
fetch(url[, options])
url
A string representing the URL for fetchingoptions
Options for the HTTP(S) request- Returns:
Promise<[Response](#class-response)>
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:
Header | Value |
---|---|
Accept-Encoding | gzip,deflate (when options.compress === true ) |
Accept | */* |
Connection | close (when no options.agent is present) |
Content-Length | (automatically calculated, if possible) |
Transfer-Encoding | chunked (when req.body is a stream) |
User-Agent | node-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 anotherRequest
(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)
body
AString
orReadable
streamoptions
AResponseInit
options dictionary
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 theHeaders
object
构造一个新的 Headers
对象。 init
可以是 null
、Headers
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 Request
和 Response
类。
目前node-fetch中还没有实现以下方法:
formData()
body.body
(deviation from spec)
- Node.js
Readable
stream
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
流。
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<Buffer>
使用正文并返回将解析为 Buffer 的承诺。
body.textConverted()
(node-fetch extension)
- Returns:
Promise<String>
与 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
的 abort
事件。 它具有 AbortError
的 name
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 和@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
A light-weight module that brings window.fetch
to Node.js
(We are looking for v2 maintainers and collaborators)
- Motivation
- Features
- Difference from client-side fetch
- Installation
- Loading and configuring the module
- Common Usage
- Advanced Usage
- API
- License
- Acknowledgement
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()
andres.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 fetchingoptions
Options for the HTTP(S) request- Returns:
Promise<[Response](#class-response)>
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:
Header | Value |
---|---|
Accept-Encoding | gzip,deflate (when options.compress === true ) |
Accept | */* |
Connection | close (when no options.agent is present) |
Content-Length | (automatically calculated, if possible) |
Transfer-Encoding | chunked (when req.body is a stream) |
User-Agent | node-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 anotherRequest
(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)
body
AString
orReadable
streamoptions
AResponseInit
options dictionary
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 theHeaders
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)
- Node.js
Readable
stream
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<Buffer>
Consume the body and return a promise that will resolve to a Buffer.
body.textConverted()
(node-fetch extension)
- Returns:
Promise<String>
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