jquery,javascript -设置某一ul下的li下的 a的属性

//javascript
var ul = document.getElementById('ul);
var as = ul.getElementsByTagName('a');
for(var i = 0; i <as.length; i++) {
    as.item(i).onmouseover = function() {
	    var iframe_con = document.getElementById(pos_content);
	    var src = './content/' + this.innerHTML + '.html';
	    iframe_con.setAttribute('src', src);
	    console.log(src);
	}
}

//jquery
 $("#um_div li a").mouseover(function () {
	$("#" + pos_content + "_content").attr('src', 'content/' + this.innerHTML + ".html");
});