[Js/DOM] getElementsByAttirbute, getElementsByClass

// DOM utility
document.getElementsByAttribute = function (attr, val, tag) {
 if (attr == "class") {
  return document.getElementsByClass(val, tag);
 }
 var a = new Array();
 tag = (tag) ? tag : "*";
 var els = document.getElementsByTagName(tag);
 for (i = 0; i < els.length; i++) {
  if (els[i].getAttribute(attr) == val) {
   a[a.length] = els[i];
  }
 }
 return a;
};

// ref. http://www.dustindiaz.com/getelementsbyclass/
document.getElementsByClass = function (val, tag) {
 var a = new Array();
 var tag = (tag) ? tag : "*";
 var els = document.getElementsByTagName(tag);
 var pattern = new RegExp("(^|\\s)" + val + "(\\s|$)");
 for (i = 0; i < els.length; i++) {
  if (pattern.test(els[i].className)) {
   a[a.length] = els[i];
  }
 }
 return a;
};