DOM 방법

    
    
    



    
    window.onload=function () {
        var ul1=document.getElementById('ul1');
        var aLi=getElementsByClassName(ul1,'li','box');
        console.log(aLi);
        function getElementsByClassName(parent,tagName,className) {
            var aEls=parent.getElementsByTagName(tagName);
            var arr=[];
            for (var i = 0; i < aEls.length; i++) {
                var aClassName=aEls[i].className.split(' ');
                for (var j = 0; j < aClassName.length; j++) {
                    if (aClassName[j]==className) {
                        arr.push(aEls[i]);
                        break;
                    }
                }
            
        }
        return arr;
    }
}
    
    

        
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    window.onload=function () {
        var odiv=document.getElementById('div1');
        addclass(odiv,'box3');
       function addclass(obj,className) {
           if (!obj.className) {
               obj.className=className;
           }
           else  {
            var arrClassName=obj.className.split(' ');

            var _index=arrIndexOf(arrClassName,className);
            if (_index==-1) {
                obj.className+=' '+className;
            }
               
           }
       }
       function removeclass(obj,className) {
           if (obj.className) {
              var arrClassName=obj.className.split(' ');
              var _index=arrIndexOf(arrClassName,className);
              if (_index!=-1) {
                  arrClassName.splice(_index, 1)
                  obj.className=arrClassName.join(' ');
              }
           }
       }
       removeclass(odiv,'box');
       function arrIndexOf(arr,v) {
            for (var i = 0; i < arr.length; i++) {
                if (arr[i]==v) {
                     return i;
                 } 
                 
            }
            return -1;

          
       }
    }