js简单自定义事件与主动触发事件

 1 var events = {
 2     addHandler: function (element, eventType, handler) {
 3         if (element.addEventListener) {
 4             return element.addEventListener(eventType, handler, false);
 5         } else {
 6             return element.attachEvent("on" + eventType, handler);
 7         }
 8     },
 9     removeHandler: function (element, eventType, handler) {
10         if (element.removeEventListener) {
11             return element.removeEventListener(eventType, handler, false);
12         } else {
13             return element.detachEvent("on" + eventType, handler);
14         }
15     },
16     getEvent: function (event) {
17         return event || window.event;
18     },
19 }

//执行鼠标进入事件
document.querySelector('#test').dispatchEvent(new Event('mouseenter'))