js根据className得到数组

    function getElementsByClassName (className) {
    var all = document.all ? document.all : document.getElementsByTagName('*');
    var elements = new Array();
      alert(all.length);
    for (var e = 0; e < all.length; e++) {
      if (all[e].className == className) {
        elements[e] = all[e];
        alert(elements.length);
        break;
      }
    }
    alert(elements.length);
    return elements;
   }