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.

Note: This feature is available in Web Workers

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

BCD tables only load in the browser

See also