Headers: has() method
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
js
has(name)
Parameters
name-
The name of the HTTP header you want to test for. If the given name is not a valid HTTP header name, this method throws a
TypeError.
Return value
A boolean value.
Examples
Creating an empty Headers object is simple:
js
const myHeaders = new Headers(); // Currently empty
You could add a header to this using Headers.append, then test for the
existence of it using has():
js
myHeaders.append("Content-Type", "image/jpeg");
myHeaders.has("Content-Type"); // Returns true
myHeaders.has("Accept-Encoding"); // Returns false
Specifications
| Specification |
|---|
| Fetch Standard # ref-for-dom-headers-has① |
Browser compatibility
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