JS操作select下拉框动态变动(创建/删除/获取)

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

function addOption(){
//根据id查找对象，
var obj=document.getElementByIdx_x('mySelect');
//添加一个选项
obj.add(new Option("文本","值"));
}

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

function removeOne(){
var obj=document.getElementByIdx_x('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.getElementByIdx_x('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.getElementByIdx_x('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.getElementByIdx_x('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.getElementByIdx_x("mySelect");
mySelect.parentNode.removeChild(mySelect);
}