JavaScript 原生实现事件绑定与委托机制

/**
 * addEvent
 * author laynezhou@tencent.com
 */
window.Event = {};
var Event = {

  funcList: {}, //保存delegate所绑定的方法  
  ieFuncList: {}, //由于保存在ie下绑定的方法


  on: function(obj, selector, type, fn) {
    if (!obj || !selector) return false;
    var fnNew = Event.delegateHandle(obj, selector, fn);
    Event.addEvent(obj, type, fnNew);
    /* 将绑定的方法存入Event.funcList，以便之后解绑操作 */
    if (!Event.funcList[selector]) {
      Event.funcList[selector] = {};
    }
    if (!Event.funcList[selector][type]) {
      Event.funcList[selector][type] = {};
    }

    Event.funcList[selector][type][fn] = fnNew;
  },

  off: function(obj, selector, type, fn) {
    if (!obj || !selector || !Event.funcList[selector]) {
      return false;
    }
    var fnNew = Event.funcList[selector][type][fn];
    if (!fnNew) {
      return;
    }

    Event.offEvent(obj, type, fnNew);
    Event.funcList[selector][type][fn] = null;
  },

  delegateHandle: function(obj, selector, fn) {
    /* 实现delegate 的转换方法，事件冒泡上升时, 符合条件时才会执行回调函数 */
    var func = function(event) {
      var event = event || window.event;
      var target = event.srcElement || event.target;
      var parent = target;

      function contain(item, elmName) {
        if (elmName.split('#')[1]) { //by id
          if (item.id && item.id === elmName.split('#')[1]) {
            return true;
          }
        }
        if (elmName.split('.')[1]) { //by class
          if (hasClass(item, elmName.split('.')[1])) {
            return true;
          }
        }
        if (item.tagName == elmName.toUpperCase()) {
          return true; //by tagname
        }
        return false;
      }
      while (parent) {
        /* 如果触发的元素，属于(selector)元素的子级。 */
        if (obj == parent) {
          return false; //触发元素是自己
        }
        if (contain(parent, selector)) {

          fn.call(obj, event);
          return;
        }
        parent = parent.parentNode;
      }
    };
    return func;
  },
  addEvent: function(target, type, fn) {
    if (!target) return false;
    var add = function(obj) {
      if (obj.addEventListener) {

        obj.addEventListener(type, fn, false);

      } else {
        // for ie
        if (!Event.ieFuncList[obj]) Event.ieFuncList[obj] = {};
        if (!Event.ieFuncList[obj][type]) Event.ieFuncList[obj][type] = {};
        Event.ieFuncList[obj][type][fn] = function() {
          fn.apply(obj, arguments);
        };
        obj.attachEvent("on" + type, Event.ieFuncList[obj][type][fn]);
      }
    }
    if (target.length >= 0 && target !== window && !target.tagName) {
      for (var i = 0, l = target.length; i < l; i++) {
        add(target[i])
      }
    } else {
      add(target);
    }
  },


  offEvent: function(target, type, fn) {
    if (!target) return false;
    var remove = function(obj) {
      if (obj.addEventListener) {
        obj.removeEventListener(type, fn, false);

      } else {
        //for ie
        if (!Event.ieFuncList[obj] || !Event.ieFuncList[obj][type] || !Event.ieFuncList[obj][type][fn]) {
          return;
        }
        obj.detachEvent("on" + type, Event.ieFuncList[obj][type][fn], false);
        Event.ieFuncList[obj][type][fn] = {};
      }
    }
    if (target.length >= 0 && target !== window && !target.tagName) {
      for (var i = 0, l = target.length; i < l; i++) {
        remove(target[i])
      }
    } else {
      remove(target);
    }
  },

};

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>test</title>
</head>
<body>
<p>测试 Event </p>
<div id=content>
  <ul>
    <li><button id="btn1">1</button></li>
    <li><button id="btn2">2</button></li>
    <li><button id="btn3">3</button></li>
    <li><button id="btn4">4</button></li>
    <li><button id="btn5">5</button></li>
  </ul>

<button id="unbind">取消绑定</button>
</div>
<p id="text"></p>

<script src="addEvent.js"></script>
<script>
(function(){
  /* 演示demo*/
  var $id=function(id)
  {
    return document.getElementById(id) || id;
  }
  var outer = $id("content"),
    btn = $id("text");
  Event.on(outer,'button',"click",add);
  Event.on(outer,'#unbind',"click",remove);

  //动态添加一个按钮,查看是否有事件响应
  var newbtn = document.createElement("button");
  var node = document.createTextNode("new button");
  newbtn.appendChild(node);
  outer.appendChild(newbtn);

  function add(){
    var e = arguments[0] || window.event;
    var target = e.srcElement || e.target;
    console.log("target:",target);
    btn.innerHTML = target.innerHTML + ' ' + e.type;
  }
  function remove(){
    Event.off(outer,'button',"click",add);
    Event.off(outer,'#unbind',"click",remove);
  }
})();
</script>
</body>
</html>