Intercept any XMLHttpRequests happening in your page either by your own code or from a third party library

intercept-XMLHttpRequest.js

  (function(originalOpen) {
    XMLHttpRequest.prototype.open = function() {
      this.addEventListener('progress', function() {
        console.log('request in progress);
      });
      this.addEventListener('load', function() {
        console.log('request complete);
      });
      originalOpen.apply(this, arguments);
    };
  })(XMLHttpRequest.prototype.open);