求关于javascript 内容替换的方法

<script>

function changeSrc(arr){

  var eles = document.all.tags("img");

  for(i in eles){

    eles[i].src = arr[i];

  }

}

var arr = new Array();

arr[0] = "1";

arr[1] = "2";

arr[2] = "3";

arr[3] = "4";

window.onload=function(){

changeSrc(arr);

}

</script>

<div>aaa<br/><img src="1.jpg" pid="0"/><img src="2.jpg" pid="1"/><img src="3.jpg" pid="2"/><img src="11.jpg"/><img src="121.jpg"/><img src="31.jpg"/>adsfads
adsf<img src="11.jpg"/>
</div>