转自：http://blog.csdn.net/a313976010/article/details/6728646

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1.动态创建select

function createSelect(){
          var mySelect = document.createElement("select");
          mySelect.id = "mySelect"; 
          document.body.appendChild(mySelect);
      }

2.添加选项option

 function addOption(){

          //根据id查找对象，
           var obj=document.getElementById('mySelect');

           //添加一个选项
           obj.add(new Option("文本","值"));    //这个只能在IE中有效
           obj.options.add(new Option("text","value")); //这个兼容IE与firefox
     }

3.删除所有选项option

  function removeAll(){
           var obj=document.getElementById('mySelect');
           obj.options.length=0;

     }

4.删除一个选项option

function removeOne(){
           var obj=document.getElementById('mySelect');

           //index,要删除选项的序号，这里取当前