# Introduction to AJAX

AJAX technology is a way to update part of a page without completely reloading it. The technology is based on JavaScript, the HTTP protocol, and some server part, for example, PHP, NodeJS, or some other.

Currently, AJAX is handled through `fetch`. This is modern technology, but doesn't work in older browsers. An older technique is to use the `XMLHttpRequest` object. You may still encounter this technology, but you shouldn't delve into it too much.

To learn how AJAX works, you need a server. We will use our training server. Let's make an HTML file in the folder with the server, which we will open in the browser:

`<!DOCTYPE html> <html> <head> <title></title> <script src="client.js" defer></script> </head> <body> </body> </html>`

Link a JavaScript file to it:

`alert('test');`

Create the described files and check their operation in the browser.

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