code: function XMLHttpRequestEvent(xhr, type) {
      this.type = type;
      this.bubbles = false;
      this.cancelable = false;
      this.timeStamp = now();
  
      this.isTrusted = false;
      this.defaultPrevented = false;
  
      // Event phase should be "AT_TARGET"
      // https://dom.spec.whatwg.org/#dom-event-at_target
      this.eventPhase = 2;
  
      this.target = xhr;
      this.currentTarget = xhr;
    }
docs: Event object https://dom.spec.whatwg.org/#concept-event