JS动态添加option和删除option

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

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 
} 

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

function removeOne(){ 
    var obj=document.getElementById(‘mySelect‘); 
    //index,要删除选项的序号，这里取当前选中选项的序号 
    var index=obj.selectedIndex; 
    obj.options.remove(index); 
} 

var obj=document.getElementById(‘mySelect‘); 
var index=obj.selectedIndex; //序号，取当前选中选项的序号 
var val = obj.options[index].value; 

var obj=document.getElementById(‘mySelect‘); 
var index=obj.selectedIndex; //序号，取当前选中选项的序号 
var val = obj.options[index].text; 

var obj=document.getElementById(‘mySelect‘); 
var index=obj.selectedIndex; //序号，取当前选中选项的序号 
var val = obj.options[index]=new Option("新文本","新值"); 

function removeSelect(){ 
    var mySelect = document.getElementById("mySelect"); 
    mySelect.parentNode.removeChild(mySelect); 
}