运用 JS 实现 select 动态添加 option

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")); //方法一
obj.options.add(new Option("text", "value")); //方法二
for(var i = 0; i < 10; i++) {
obj.options[i] = new Option("新文本", "新值"); //方法三
}
}

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');
var index = obj.selectedIndex; //index,要删除选项的序号
obj.options.remove(index);
}

5.获得选项 option 的值

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;

6.获得选项 option 的文本

var obj = document.getElementById('mySelect');
var index = obj.selectedIndex;
var val = obj.options[index].text;

7.修改选项 option

var obj = document.getElementById('mySelect');
var index = obj.selectedIndex;
var val = obj.options[index] = new Option("新文本", "新值");

8.删除 select

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

参考链接：
https://msdn.microsoft.com/en-us/library/dd757810(v=vs.85).aspx
http://www.cnblogs.com/duanhuajian/archive/2013/06/09/3129365.html
http://www.javascriptkit.com/jsref/select.shtml