Css:

#click-wrap{
    width: 900px;height: 30px;background: #fc0;}button{
    display: inline-block;width: 180px;height: 30px;line-height: 30px;text-align: left;padding: 0 20px;cursor: pointer;}

HTML :

　　
      
        
       click me: 0         
       click me too: 0         
       click me three: 0     
      

JS :

　　var wrap = document.getElementById("click-wrap");    function addEvent(el, type, fn){        if(document.body.addEventListener){            addEvent = function(el, type, fn){                console.log(00)                el.addEventListener(type, fn, false);            };        }else{            addEvent = function(el, type, fn){                el.attachEvent("on" + type, function(){                    fn.apply(el, arguments);                });            };        }        addEvent(el, type, fn);    };    function myHandler(e){        console.log(11)        var src, parts;        // 获取事件和源元素        e = e || window.event;        src = e.target || e.srcElement;        if(src.nodeName.toLowerCase() !== "button"){            return;        }        // 实际工作：升级标签        parts = src.innerHTML.split(": ");        parts[1] = parseInt(parts[1], 10) + 1;        src.innerHTML = parts[0] + ": " + parts[1];        // 无冒泡        if(typeof e.stopPropagation === "function"){            e.stopPropagation();        }        if(typeof e.cancelBubble !== "undefined"){            e.cancelBubble = true;                    }        // 阻止默认操作        if(typeof e.preventDefault === "function"){            e.preventDefault();        }        if(typeof e.returnValue !== "undefined"){            e.returnValue = false;        }    }    addEvent(wrap, "click", myHandler);

 

 再次复习了事件委托，addEvent先写好了，也知道原理，但有个if else 我就直接写的return 导致后面的语句addEvent(el, type, fn)没有执行 0.0 好粗心