AJAX = Asynchronous JavaScript And XML.
Concept of Ajax is – Stop page reloading. Idea is — To use JS to make request to server and take XML data returned and use it!
Later on XML is replaced by JSON & XMLHttpRequest is replaced by Fetch.
Microsoft introduce ActiveXObject to deal with Java conflicts. Later on it is changed to XMLHttpRequest object.
Ajax is not a programing language or not a single method.
Ajax is a principles (set of rules) to use JavaScript code to get dynamic data Asynchronously.
Asynchronous – We are not waiting for any set of code to complete. Means we can execute multiple set of code as same time.
Synchronous – One thing at a time only. If I perform some task, I have to wait until the process is completed.
To know Ajax completely you have to know:
- What is HTTP protocols?
- JSON & XML basics
- What is Asynchronous & Synchronous call?
- Constructor function in JavaScript
- XMLHttpRequest object with importance of new keyword