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The has() method of the Headers interface returns a boolean stating whether a Headers object contains a certain header.

For security reasons, some headers can only be controller by the user agent. These headers include the forbidden header names  and forbidden response header names.

Syntax

myHeaders.has(name);

Parameters

name
The name of the HTTP header you want to test for. If the given name is not the name of an HTTP header, this method throws a TypeError.

Returns

A Boolean.

Example

Creating an empty Headers object is simple:

var myHeaders = new Headers(); // Currently empty

You could add a header to this using Headers.append, then test for the existence of it using has():

myHeaders.append('Content-Type', 'image/jpeg');
myHeaders.has('Content-Type'); // Returns true
myHeaders.has('Accept-Encoding'); // Returns false

Specifications

Specification Status Comment
Fetch
The definition of 'has()' in that specification.
Living Standard  

Browser compatibility

Feature Chrome Edge Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support 42
41 behind pref
 
(Yes) 39 (39)
34 behind pref
No support

29
28 behind pref

No support
Feature Android Edge Firefox Mobile (Gecko) Firefox OS (Gecko) IE Phone Opera Mobile Safari Mobile Chrome for Android
Basic support No support (Yes) No support No support No support No support No support No support

See also

Document Tags and Contributors

 Contributors to this page: chrisdavidmills, erikadoyle, jpmedley, kscarfone
 Last updated by: chrisdavidmills,