fakeXHR

A small XMLHttpRequest wrapper for intercepting or faking responses. The module is plain untranspiled es6.

Installation

npm i -S fakexhr

Usage

When loaded will take over window.XMLHttpRequest. The original class will be stored at window.XMLHttpRequest.original.

The new XMLHttpRequest is baseclassed from the real one so it will work the same.

The XHR instances will have an extra method called fake.

Faking the XHR response

The first parameter is the string you want the response to be. The remaining parameters are the exact same signature as you will use in xhr.open(..,).

const xhr = new XMLHttpRequest()
xhr.fake('<foo>bar</foo>', 'GET', 'file.xml')
xhr.open('GET', 'file.xml')
xhr.send()

This will fake the xhr.responseText only for this xhr instance. To fake the responses for all instances you can use the similarly named static method.

XMLHttpRequest.fake('<foo>bar</foo>', 'GET', 'file.xml')

const xhr = new XMLHttpRequest()
xhr.open('GET', 'file.xml')
xhr.send()

Contrary to hijacking a response, faking it will not send an actual HTTP request. This also means the fired events will have the isTrusted property set to false.

Hijacking the XHR response

To alter an existing request you can hijack it by overloading the same to methods. Simply replace the first parameter with a callback function.

const xhr = new XMLHttpRequest()
xhr.fake(xml=>`<blaat>${xml}</blaat>`, 'GET', 'file.xml')
xhr.open('GET', 'file.xml')
xhr.send()

The same applies to the static method.