Headers extension type

The Headers interface of the Fetch API allows you to perform various actions on HTTP request and response headers. These actions include retrieving, setting, adding to, and removing headers from the list of the request's headers.

A Headers object has an associated header list, which is initially empty and consists of zero or more name and value pairs. You can add to this using methods like Headers.append (see Examples.) In all methods of this interface, header names are matched by case-insensitive byte sequence.

For security reasons, some headers can only be controlled by the user agent. These headers include the and .

A Headers object also has an associated guard, which takes a value of immutable, request, request-no-cors, response, or none. This affects whether the Headers.set, Headers.delete, and Headers.append methods will mutate the header. For more information see .

You can retrieve a Headers object via the Request.headers and Response.headers properties, and create a new Headers object using the Headers.Headers constructor.

An object implementing Headers can directly be used in a for...of structure, instead of Headers.entries: for (const p of myHeaders) is equivalent to for (const p of myHeaders.entries()).

Note: you can find out more about the available headers by reading our HTTP headers reference.

on

• JSObject

Implemented types

• JSObject

Constructors

Headers([HeadersInit init])

factory

Properties

hashCode → int

The hash code for this object.

no setter, inherited

runtimeType → Type

A representation of the runtime type of the object.

no setter, inherited

Methods

append(String name, String value) → void

The append() method of the Headers interface appends a new value onto an existing header inside a Headers object, or adds the header if it does not already exist.

delete(String name) → void

The delete() method of the Headers interface deletes a header from the current Headers object.

get(String name) → String?

The get() method of the Headers interface returns a byte string of all the values of a header within a Headers object with a given name. If the requested header doesn't exist in the Headers object, it returns null.

getSetCookie() → JSArray<JSString>

The getSetCookie() method of the Headers interface returns an array containing the values of all headers associated with a response. This allows Headers objects to handle having multiple Set-Cookie headers, which wasn't possible prior to its implementation.

has(String name) → bool

The has() method of the Headers interface returns a boolean stating whether a Headers object contains a certain header.

noSuchMethod(Invocation invocation) → dynamic

Invoked when a nonexistent method or property is accessed.

inherited

set(String name, String value) → void

The set() method of the Headers interface sets a new value for an existing header inside a Headers object, or adds the header if it does not already exist.

toString() → String

A string representation of this object.

inherited

Operators

operator ==(Object other) → bool

The equality operator.

inherited