常見寫法

1 let addEvent = (ele, type, handler) => {
2     if (window.addEventListener) {
3         return ele.addEventListener(type, handler, false);
4     }
5     if (window.attachEvent) {
6         return ele.attachEvent(`on${type}`, handler);
7     }
8 };

嗅探

 1 let addEvent = (() => {
 2     if
 
 (window.addEventListener) {
 3         return function (ele, type, handler) {
 4             ele.addEventListener(type, handler, false);
 5         };
 6     }
 7     if (window.attachEvent) {
 8         return function (ele, type, handler) {
 9             ele.attachEvent(`on${type}`, handler);
10         };
 
11     }
12 })();

惰性載入

 1 let addEvent = (ele, type, handler) => {
 2     if (window.addEventListener) {
 3         addEvent = function (ele, type, handler) {
 4             ele.addEventListener(type, handler, false);
 5         };
 6     }
 7     if (window.attachEvent) {
 8         addEvent = function
 
 (ele, type, handler) {
 9             ele.attachEvent(`on${type}`, handler);
10         };
11     }
12     addEvent(ele, type, handler);
13 };