Question

How to check if an ajax function is busy from a previous call? How can i prevent the call to an ajax function if it’s readyState != 4 yet from a previous call?

Answer 1

You can use a boolean and an appropriate onreadystatechange functoin;

var inprogress = true;
ajaxRequest = ...
ajaxRequest.onreadystatechange = function(){
    if(ajaxRequest.readyState == 4){
        inprogress = false;
    }
}