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JavaScript AJAX Basics (retiring) AJAX Concepts A Simple AJAX Example

Arsalan Raja
Arsalan Raja
6,508 Points
Posted by Arsalan Raja
Arsalan Raja
6,508 Points

Question about variable var xhr = new XMLHttpRequest();

in this video in javascript code Dave create new instance and stored in variable xhr. I didnt understand why did he create new instance and as i know you can create instance from constructor function and there is no constructor function.

1 Answer

Gabriel D. Celery
Gabriel D. Celery
13,810 Points
Gabriel D. Celery
Gabriel D. Celery
13,810 Points

All modern browsers have a "built-in" function called XMLHttpRequest(). Since its built-in you don't have to define it anywhere. Its an object constructor and you use it to create an object that can be used to exchange data with a server behind the scenes. (Since AJAX isn't simply JavaScript running in your browser).

Maria Campbell
Maria Campbell
8,641 Points
Maria Campbell
Maria Campbell
8,641 Points

That is not true. I followed Dave exactly in the work spaces, and nothing happened. I got an error in the JS Console that stated:

Uncaught ReferenceError: XMLHTTPRequest is not defined

referring to the code:

var xhr = new XMLHTTPRequest();

Now why is THAT happening?