js 循环BUG

<div>1</div>
<div>2</div>
<script type="text/javascript">
var elements = document.getElementsByTagName("div");
for (var i = 0; i<elements.length; i++) {
//	elements[i].onclick=function(){
//		alert("Div number " + elements[i].innerHTML); //在遍历数组时对DOM监听事件，索引值始终等于遍历结束后的值（数组长度）
//	}
    elements[i].onclick = 
	(function(idx) {          //闭包，正确显示
    	return function() {   
            alert("Div number " + elements[idx].innerHTML);  
        }
    })(i);
}
for (var i = 0; i<elements.length; i++) {
	elements[i]._index=i;
	elements[i].onclick=function(){
		alert("Div number " + elements[this._index].innerHTML);
	}
}
</script>