外观模式即让多个⽅法⼀起被调⽤
涉及到兼容性，参数⽀持多格式，有很多这种代码，对外暴露统⼀的api，⽐如上⾯的$on ⽀持数组，￥offff参数⽀持多个情况， 对⾯只⽤⼀个函数，内部判断实现
⾃⼰封装组件库 经常看到
myEvent = {
stop: function(e) {
if (typeof e.preventDefault() === "function") {
e.preventDefault();
}
if (typeof e.stopPropagation() === "function") {
e.stopPropagation();
}
//for IE
if (typeof e.returnValue === "boolean") {
e.returnValue = false;
}
if (typeof e.cancelBubble === "boolean") {
e.cancelBubble = true;
}
}
addEvent(dom, type, fn) {
if (dom.addEventListener) {
dom.addEventListener(type, fn, false);
} else if (dom.attachEvent) {
dom.attachEvent('on' + type, fn);
} else {
dom['on' + type] = fn;
}
}
}