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This is an experimental technology
Because this technology's specification has not stabilized, check the compatibility table for the proper prefixes to use in various browsers. Also note that the syntax and behavior of an experimental technology is subject to change in future versions of browsers as the spec changes.
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 | Firefox (Gecko) | Internet Explorer | Opera | Safari (WebKit) |
|---|---|---|---|---|---|
| Basic support | 42 41 behind pref |
39 (39) 34 behind pref |
Not supported |
29 |
Not supported |
| Feature | Android | Firefox Mobile (Gecko) | Firefox OS (Gecko) | IE Phone | Opera Mobile | Safari Mobile | Chrome for Android |
|---|---|---|---|---|---|---|---|
| Basic support | Not supported | Not supported | Not supported | Not supported | Not supported | Not supported | Not supported |