JS中getElementsByClassName与classList兼容性问题解决方案分析

<body>
    <p class="p1 p">p1 p</p>
    <p class="p"> p</p>
    <script type="text/javascript">
        var aP = document.getElementsByClassName(' p p1' );
        alert(aP.length);
        /*标准 ： 1*/
        /*非标准：Error:对象不支持“getElementsByClassName”属性或方法*/
    </script>
</body>

var getElementsByClassName = (function (classList,/*optional*/parent){
    if(typeof classList !== "string") throw TypeError("the type of classList is error");
    var parent = parent || window.document;/*添加默认值*/
    if(parent.getElementsByClassName){/*如果是标准浏览器支持该方法*/
      return parent.getElementsByClassName(classList);
    }else{/*如果不支持该方法即非标准浏览器*/
      var child = parent.getElementsByTagName("*");
      var nodeList = [];
      /*获得classList的每个类名 解决前后空格 以及两个类名之间空格不止一个问题*/
      var classAttr = classList.replace(/^\s+|\s+$/g,"").split(/\s+/);
      for(var j = 0,len_j = child.length; j<len_j; j++){
        var element = child[j];
        for(var i = 0,len_i = classAttr.length; i< len_i; i++){
          var _className = classAttr[i];
          if(element.className.search(new RegExp("(\\s+)?"+_className+"(\\s+)?")) === -1){
            break;
          }
        }
        if(i===len_i) nodeList.push(element);
      }
      return nodeList;
    }
});

var classList = null;
(function(){
    classList = function (obj){
      this.obj = obj;
    };
    classList.prototype.add = function(value){
      if(typeof value !== "string") throw TypeError("the type of value is error");
      if(this.obj.classList){
        this.obj.classList.add(value);
      }else{
        var arr = value.replace(/^\s+|\s+$/g,"").split(/\s+/);
        this.obj.classList +=" "+arr.join(" ");
      }
    };
    classList.prototype.contains = function(value){
      if(typeof value !== "string") throw TypeError("the type of value is error");
      if(this.obj.classList){
        return this.obj.classList.contains(value);
      }else{
        var arr = value.replace(/^\s+|\s+$/g,"").split(/\s+/);
        var _className = this.obj.className;
        for(var i = 0,len= arr.length; i<len; i++){
          if(_className.search(new RegExp("(\\s+)?"+arr[i]+"(\\s+)?"))===-1){
            return false;
          }
        }
        return true;
      }
    };
    classList.prototype.remove = function(value){
      if(typeof value !== "string") throw TypeError("the type of value is error");
      if(this.obj.classList){
        return this.obj.classList.remove(value);
      }else{
        var arr = value.replace(/^\s+|\s+$/g,"").split(/\s+/);
        var _className = this.obj.className;
        for(var i = 0, len = arr.length;i<len; i++){
          if(_className.search(new RegExp("(\\s+)?"+arr[i]+"(\\s+)?"))!==-1){
            _className = _className.replace(new RegExp("(\\s+)?"+arr[i]+"(\\s+)?"),"");
          }
        }
        this.obj.className = _className;
      }
    };
    classList.prototype.toggle = function(value){
      if(typeof value !== "string") throw TypeError("the type of value is error");
      if(this.contains(value)){
        this.remove(value);
      }else{
        this.add(value);
      }
    };
})();