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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 controlled 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

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support

42

412

Yes

39

343

No

29

284

No
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support

42

411

42

412

Yes No

29

284

No4.0

1. From version 41: this feature is behind the Experimental Web Platform Features preference.

2. From version 41: this feature is behind the Experimental Web Platform Features preference. To change preferences in Chrome, visit chrome://flags.

3. From version 34: this feature is behind the dom.fetch.enabled preference. To change preferences in Firefox, visit about:config.

4. From version 28: this feature is behind the Experimental Web Platform Features preference.

See also

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