详解js的事件代理（委托）

var addEvent = (function () {
 if (document.addEventListener) {
 return function (element, type, handler) {
 element.addEventListener(type, handler, false);
 };
 } else if (document.attachEvent) {
 return function (element, type, handler) {
 element.attachEvent('on' + type, function () {
 handler.apply(element, arguments);
 });
 };
 } else {
 return function (element, type, handler) {
 element['on' + type] = function () {
 return handler.apply(element, arguments);
 };
 };
 }
})(),
getClassElements = function (parentElement, classname) {
 var all, element, classArr = [], classElements = [];
 if (parentElement.getElementsByClassName) {
 return parentElement.getElementsByClassName(classname);
 } else {
 all = parentElement.getElementsByTagName('*');
 for (var i = 0, len = all.length; i < len; i++) {
 element = all[i];
 classArr = element && element.className && element.className.split(' ');
 if (classArr) {
 for (var j = 0; j < classArr.length; j++) {
  if (classArr[j] === classname) {
  classElements.push(element);
  }
 }
 }
 }
 return classElements;
 }
},
delegate = function () { // 参数：element, type, [selector,] handler
 var args = arguments,
 element = args[0],
 type = args[1],
 handler;
 if (args.length === 3) {
 handler = args[2];
 return addEvent(element, type, handler);
 }
 if (args.length === 4) {
 selector = args[2];
 handler = args[3];
 return addEvent(element, type, function (event) {
 var event = event || window.event,
 target = event.target || event.srcElement,
 quickExpr = /^("htmlcode">

handler.apply(idElement, arguments);
handler.apply(elements[count], arguments);




测试一下：


<style>
#outer {padding: 50px; background-color: lightpink;}
#inner {padding: 30px; background-color: aliceblue;}
#paragraph1, #paragraph3 {background-color: cadetblue}
</style>




<div id="outer">outer
 <div id="inner">inner
 <p id="paragraph1" class="parag1">paragraph1</p>
 <p id="paragraph2" class="parag">paragraph2</p>
 <span>span</span>
 <p id="paragraph3" class="parag">paragraph3</p>
 </div>
</div>




var outer = document.getElementById('outer');
delegate(outer, 'click', function () {
 console.log(this.id); // outer
});





delegate(outer, 'click', 'p', function () {
 console.log(this.id); //点击 paragraph1 元素，输出其id为 "paragraph1"
});


模仿 jQuery 的风格，优化代码：


(function () {
 var $ = function (element) {
 return new _$(element);
 };
 var _$ = function (element) {
 this.element = element && element.nodeType === 1 "htmlcode">

var outer = document.getElementById('outer');
$(outer).delegate('click', '.parag', function (event) {
 console.log(this.id);
});


以上就是本文的全部内容，希望本文的内容对大家的学习或者工作能带来一定的帮助，同时也希望多多支持！