Headers: has() method

Note: This feature is available in Web Workers.

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 request headers 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

See also