var getElementsByClassName = function (searchClass, node,tag) {   if(document.getElementsByClassName){ //原生    var nodes =  (node || document).getElementsByClassName(searchClass),result = [];      for(var i=0 ;node = nodes[i++];){//多个class检索        if(tag !== "*" && node.tagName === tag.toUpperCase()){          result.push(node)        }      }      return result    }else{      node = node || document;      tag = tag || "*";      var classes = searchClass.split(" "),      elements = (tag === "*" && node.all)? node.all : node.getElementsByTagName(tag),      patterns = [],      current,      match;      var i = classes.length;      while(--i >= 0){        patterns.push(new RegExp("(^|\\s)" + classes[i] + "(\\s|$)"));      }      var j = elements.length;      while(--j >= 0){        current = elements[j];        match = false;        for(var k=0, kl=patterns.length; k