Headers

`Headers`

Creates a new Headers object for managing HTTP request and response headers

Syntax

JavaScript

new Headers(init?)

Parameters

Parameter	Type	Description
init	HeadersInit	An object, array of key-value pairs, or existing Headers to initialize from

Return Value

A new Headers object

Examples

Basic Usage

const headers = new Headers()
headers.set('Content-Type', 'application/json')
headers.set('Authorization', 'Bearer token123')
console.log(headers.get('Content-Type'))

Practical Example

const headers = new Headers({
  'Content-Type': 'application/json',
  'X-Custom': 'value'
})
console.log([...headers.entries()])

Advanced Usage

function createAuthHeaders(token: string) {
  return new Headers({
    'Authorization': `Bearer ${token}`,
    'Content-Type': 'application/json',
    'Accept': 'application/json'
  })
}

Understanding Headers

The Headers method in JavaScript creates a new Headers object for managing HTTP request and response headers. It belongs to the Headers object and is one of the most widely used methods for working with headers values in modern JavaScript and TypeScript applications.

The method signature is new Headers(init?). It accepts 1 parameter: init. When called, it returns a new headers object. Understanding when and how to use Headers() helps you write more expressive, readable code.

Common use cases for Headers include data transformation, input validation, API response processing, and building reusable utility functions. It works well alongside related methods like fetch-headers-get, fetch-headers-set, fetch-headers-has, enabling you to chain operations together for complex data manipulation pipelines.

Browser support for Headers is excellent across all modern browsers including Chrome, Firefox, Safari, and Edge. It is also fully supported in Node.js and Deno. For older environments, transpilation with Babel or a polyfill may be needed.