Javascript request header get

XMLHttpRequest: getAllResponseHeaders() method

The XMLHttpRequest method getAllResponseHeaders() returns all the response headers, separated by CRLF, as a string, or returns null if no response has been received.

If a network error happened, an empty string is returned.

Note: For multipart requests, this returns the headers from the current part of the request, not from the original channel.

Syntax

Parameters

Return value

A string representing all of the response’s headers (except those whose field name is Set-Cookie ) separated by CRLF, or null if no response has been received. If a network error happened, an empty string is returned.

An example of what a raw header string looks like:

date: Fri, 08 Dec 2017 21:04:30 GMT\r\n content-encoding: gzip\r\n x-content-type-options: nosniff\r\n server: meinheld/0.6.1\r\n x-frame-options: DENY\r\n content-type: text/html; charset=utf-8\r\n connection: keep-alive\r\n strict-transport-security: max-age=63072000\r\n vary: Cookie, Accept-Encoding\r\n content-length: 6502\r\n x-xss-protection: 1; mode=block\r\n 

Each line is terminated by both carriage return and line feed characters ( \r\n ). These are essentially delimiters separating each of the headers.

Note: In modern browsers, the header names are returned in all lower case, as per the latest spec.

Examples

This example examines the headers in the request’s readystatechange event. The code shows how to obtain the raw header string, as well as how to convert it into an array of individual headers and then how to take that array and create a mapping of header names to their values.

const request = new XMLHttpRequest(); request.open("GET", "foo.txt", true); request.send(); request.onreadystatechange = () =>  if (request.readyState === this.HEADERS_RECEIVED)  // Get the raw header string const headers = request.getAllResponseHeaders(); // Convert the header string into an array // of individual headers const arr = headers.trim().split(/[\r\n]+/); // Create a map of header names to values const headerMap = >; arr.forEach((line) =>  const parts = line.split(": "); const header = parts.shift(); const value = parts.join(": "); headerMap[header] = value; >); > >; 

Once this is done, you can, for example:

const contentType = headerMap["content-type"]; 

This obtains the value of the Content-Type header into the variable contentType .

Specifications

Browser compatibility

BCD tables only load in the browser

See also

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Request: headers property

The headers read-only property of the Request interface contains the Headers object associated with the request.

Value

Examples

In the following snippet, we create a new request using the Request() constructor (for an image file in the same directory as the script), then save the request headers in a variable:

const myRequest = new Request("flowers.jpg"); const myHeaders = myRequest.headers; // Headers <> 

To add a header to the Headers object we use Headers.append ; we then create a new Request along with a 2nd init parameter, passing headers in as an init option:

const myHeaders = new Headers(); myHeaders.append("Content-Type", "image/jpeg"); const myInit =  method: "GET", headers: myHeaders, mode: "cors", cache: "default", >; const myRequest = new Request("flowers.jpg", myInit); const myContentType = myRequest.headers.get("Content-Type"); // returns 'image/jpeg' 

Specifications

Browser compatibility

BCD tables only load in the browser

See also

Found a content problem with this page?

This page was last modified on Apr 7, 2023 by MDN contributors.

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Как отправить или получить HTTP заголовки на JavaScript

05.12.18 ИТ / JavaScript 14105

Обычно для работы с заголовками используется серверный язык, однако можно попробовать использовать и JavaScript (JS).

Как отправить HTTP заголовки запроса

Отправить заголовки на JavaScript можно при помощи Ajax-запросов. На чистом языке без применения библиотек это может выглядеть так:

var request = new XMLHttpRequest(); request.open('GET', document.location, false); request.setRequestHeader('Accept', 'text/plain'); request.setRequestHeader('Content-Type', 'text/plain'); request.setRequestHeader('Content-Language', 'en-US'); request.send(null); request.getAllResponseHeaders().toLowerCase();

Как получить HTTP заголовки ответа

Получить заголовки на JavaScript задача посложней, так как это язык работает на стороне клиента. Но можно отправить запрос на сервер средствами Ajax и получить примерно похожие заголовки при помощи функции getAllResponseHeaders. Примерный код:

var request = new XMLHttpRequest(); request.open('GET', document.location, false); request.send(null); request.getAllResponseHeaders().toLowerCase();

Таким образом, отправить или получить заголовки можно и при помощи языка JavaScript, а не только при помощи серверных языков, наподобие PHP.

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