手写事件代理（兼容IE浏览器）

	<div id="btns">
		<button data-id="1">按钮1</button>
		<button data-id="2">按钮2</button>
		<button data-id="3">按钮3</button>
		<button data-id="4">按钮4</button>
		<div>666</div>
	</div>


function bindEvent(obj, type, fn) {
    
    
	if (obj.addEventListener) {
    
    
		obj.addEventListener(type, eventFn);
	} else {
    
    
		obj.attachEvent("on" + type, eventFn);
	}

	function eventFn(e) {
    
    
		var e = e || window.event;
		var target = e.target || e.srcElement;
		fn && fn.call(target,e)
	}
}
bindEvent(document.getElementById('btns'),'click',function(e){
    
    console.log(e.target.innerHTML,e.target.dataset.id)})