What is Ajax?

Ajax, or Asynchronous Javascript and XML, is used when you need to create an asynchronous request to the server, that is, run it in the background without reloading the page.

To successfully communicate on the page, you must create an XMLHttpRequest object. It acts as an intermediary between the browser and the server, which sends a request and receives data.

There are two ways to communicate with the server – GET and POST request. The first option involves accessing the document on the server, and the site URL is passed as an argument. To prevent the request from being interrupted, use the JavaScript Escape function. The second option is used when transmitting large amounts of data.

To understand whether the server has responded, you need to know the “readyState” browser property. Its values can be as follows:

• 0 – the request is not initialized;
• 1 – request setup is complete;
• 2 – the request is sent;
• 3 – the request is processed on the server;
• 4 —the request is complete.

One example of using Ajax is Google’s autocomplete feature, which offers the user keyword options as they type in the search bar. The page does not change, but the words are updated in real time.