Check for Ajax

Check for Ajax.js

// Overwrites Ajax requests on a page, used to track ajax stuff with tag manager, or to test stuff with visual website
// optimizer or optimizely
  
  function addXMLRequestCallback(callback){
    let oldSend, i;
    if( XMLHttpRequest.callbacks ) {
        // we've already overridden send() so just add the callback
        XMLHttpRequest.callbacks.push( callback );
    } else {
        // create a callback queue
        XMLHttpRequest.callbacks = [callback];
        // store the native send()
        oldSend = XMLHttpRequest.prototype.send;
        // override the native send()
        XMLHttpRequest.prototype.send = function(){
            // EDIT: I suppose you could override the onreadystatechange handler though
            for( i = 0; i < XMLHttpRequest.callbacks.length; i++ ) {
                XMLHttpRequest.callbacks[i]( this );
            }
            // call the native send()
            oldSend.apply(this, arguments);
        }
    }
  }

  
addXMLRequestCallback( function( xhr ) {
 setTimeout(function(){dothedance()}, 400);
});

// example function
  function dothedance(){
    alert('Some Ajax is going on');
  }