How to prevent multiple ajax calling

1.Call a first function before calling second function(ajax)
2.In first function , check for a div with specific id’s length
3.In second function(ajax) most top append the div with specific id.

Example:
Event Scroll to Bottom -> Call ajax:

$(window).on("scroll", function() {
     if($(window).scrollTop() == $(document).height() - $(window).height()){
            beforeajaxcalling();
    }
});

Function to be called before calling ajax:

function beforecallingajax(){
    if($("#running").length > 0){
        console.log("AJAX IS RUNNING");
    }else{
        callAjax();
    }
}

Function ajax with div(with id) appended:

function callAjax(){
    $("

“).appendTo(‘#somewhere’); —- REST OF AJAX— }