【JS】左右两个Select的左项全倒右边、左选择项到右边、右边清除选择项、右边全清四大操作

【图】

【HTML代码】

<table border="1">
    <tr>
    <td width="200px">
        <select id="leftSelect" multiple="multiple" style="width:200px;height:200px;">
        </select>
    </td>
    <td width="80px" align="center">
        <br/><br/>
        <a href="javascript:addAll();" class="btn btn-primary">&gt;&gt;</a>
        <br/><br/>
        <a href="javascript:addSelected();" class="btn btn-primary">&gt;</a>
        <br/><br/>
        <a href="javascript:removeSelected();" class="btn btn-primary">&lt;</a>
        <br/><br/>
        <a href="javascript:removeAll();" class="btn btn-primary">&lt;&lt;</a>
        <br/><br/>
    </td>
    <td width="200px">
        <select id="rightSelect" multiple="multiple" style="width:200px;height:200px;">
        </select>
    </td>
    </tr>
</table>

【JS代码】

      function addAll(){
            var leftOpts=document.getElementById("leftSelect").options;
            var rightOpts=document.getElementById("rightSelect").options;
            rightOpts.length=0;

            for(var i=0,n=leftOpts.length;i<n;i++){
                var opt=leftOpts.item(i);
                rightOpts.add(new Option(opt.text,opt.value));
            }
        }

        function removeAll(){
            var rightOpts=document.getElementById("rightSelect").options;
            rightOpts.length=0;
        }

        function addSelected(){
            var leftOpts=document.getElementById("leftSelect").options;
            var seletedArr=[];

            for(var i=0,n=leftOpts.length;i<n;i++){
                var opt=leftOpts.item(i);
                if(opt.selected){
                    seletedArr.push(new Option(opt.text,opt.value));
                }
            }

            var rightOpts=document.getElementById("rightSelect").options;
            for(var j=0;j<seletedArr.length;j++){
                var opt=seletedArr[j];

                var exist=false;
                for(var i=0,n=rightOpts.length;i<n;i++){
                    var optInner=rightOpts.item(i);
                    if(optInner.value==opt.value){
                        exist=true;
                        break;
                    }
                }

                if(exist==false){
                    rightOpts.add(new Option(opt.text,opt.value));
                }
            }

        }

        function removeSelected(){
            var rightOpts=document.getElementById("rightSelect").options;
            var n=rightOpts.length-1;
            for(var i=n;i>=0;i--){
                var opt=rightOpts[i];
                if(opt.selected==true){
                    rightOpts[i]=null;
                }
            }
        }

END