function getByClass(oParent,sClass){
var elems = oParent.getElementsByTagName("*");
var arr = [];
for(var i = 0; i < elems.length; i++ ){
if(elems[i].className == sClass ){
arr.push(elems[i]);
}
}
return arr;
}
原文：http://www.cnblogs.com/mayufo/p/4439463.html