js简单自定义事件与主动触发事件

var events = {
    addHandler: function (element, eventType, handler) {
        if (element.addEventListener) {
            return element.addEventListener(eventType, handler, false);
        } else {
            return element.attachEvent("on" + eventType, handler);
        }
    },
    removeHandler: function (element, eventType, handler) {
        if (element.removeEventListener) {
            return element.removeEventListener(eventType, handler, false);
        } else {
            return element.detachEvent("on" + eventType, handler);
        }
    },
    getEvent: function (event) {
        return event || window.event;
    },
}

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