fetch-cookie

fetch-cookie

Decorator for a fetch function to support automatic cookie storage and population.

Description

fetch-cookie wraps arround a fetch function and intercepts request options and response objects to store received cookies and populate request with the appropriate cookies.

This library is developed with Node.Js and fetch polyfill libraries such as node-fetch in mind, since the browser version is supposed to let a way to include cookies in requests. Compatibility may not be guaranteed but as long as your library implements the Fetch Standard you should be fine. In case of incompatibilities, please create a new issue.

Internally the plugin uses a cookie jar. You can insert your own (details below) but tough-cookie is preferred.

Usage

Basic

const nodeFetch = require('node-fetch')
const fetch = require('fetch-cookie')(nodeFetch)

Custom cookie jar

If you want to customize the internal cookie jar instance (for example, with a custom store), you can inject it as a second argument:

const nodeFetch = require('node-fetch')
const tough = require('tough-cookie')
const fetch = require('fetch-cookie')(nodeFetch, new tough.CookieJar())

This enables you to create multiple fetch-cookie instances that use different cookie jars, esentially two different HTTP clients with different login sessions on you backend (for example).

All calls to fetch will store and send back cookies according to the URL.

Note: All errors when setting cookies are ignored by default. You can make it to throw errors in cookies by passing a third argument (default is true).

const nodeFetch = require('node-fetch')
const tough = require('tough-cookie')
const fetch = require('fetch-cookie')(nodeFetch, new tough.CookieJar(), false) // default value is true
// false - doesn't ignore errors, throws when an error occurs in setting cookies and breaks the request and execution
// true - silently ignores errors and continues to make requests/redirections

If you use a cookie jar that is not tough-cookie, keep in mind that it must implement this interface to be compatible:

interface CookieJar {
  getCookieString(currentUrl: string, cb: (err: any, cookies: string) => void): void;
  setCookie(cookieString: string, currentUrl: string, cb: (err: any) => void, opts: { ignoreError:boolean }): void;
}

Cookies on redirects

Details: By default, cookies are not set correctly in the edge case where a response sets cookies and redirects to another URL. A real-life example of this behaviour is a login page setting a session cookie and redirecting.

The reason for this limitation is that the generic fetch API does not allow any way to hook into redirects. However, the node-fetch library does expose its own API which we can use.

TLDR: Ff cookies during indirection turns out to be a requirement for you, and if you are using node-fetch, then you can use the custom node-fetch decorator provided with this library:

const nodeFetch = require('node-fetch')
const fetch = require('fetch-cookie/node-fetch')(nodeFetch)