获取下拉列表的选定值
[英]Get the selected value of a dropdown list
问题描述
I have the follwing code. 
我有下面的代码。 I want to get the value of the selected value of the dropdownlist once the user changes it or to have the default value to be displayed by alert(). 我想在用户更改下拉列表时获取下拉列表中所选值的值，或者希望默认值由alert（）显示。 I need to use alert() from within the < body > of the html. 我需要从html的<body>中使用alert（）。 Is that possible? 那可能吗？
<html>
<head>
<title>Title</title>
<script type="text/javascript" src="phonegap-1.4.1.js">
</script> <script type="text/javascript" src="JS/Util.js"></script>
<script type="text/javascript" src="JS/Language.js"></script>
<script type="text/javascript">
function dropdown(){
var drp = document.getElementById("numberlist");
var optn = document.createElement("OPTION");
optn.text="3";
optn.value="3";
drp.add(optn);
}
</script>
</head>
<body onload="dropdown();"> <div id="main3"></div> <form><select id = "numberlist"><option>12</option><option>24</option><option>36</option></select>
4 个解决方案
解决方案1
3 2012-06-28 12:15:28
Use the code: 使用代码：
selectElement.options[ selectElement.options.selectedIndex ];
to find the index that is selected. 查找选定的索引。
So where you say var drp = document.getElementById("numberlist"); 所以说var drp = document.getElementById("numberlist"); you can now find the value of the index by doing: 您现在可以通过执行以下操作找到索引的值：
var value = drp.options[ drp.options.selectedIndex ].value;
Add the code into an onchange event so that whenever you change the selectedIndex of the element, you will be able to obtain it's value: 将代码添加到onchange事件中，以便每当更改元素的selectedIndex时，都可以获取其值：
解决方案2
2 2012-06-28 12:18:13
add this function within script tag. 在script标签内添加此功能。
function pickvalue(id){
var drp = document.getElementById(id);
alert(drp.value);
}
and add function call like this. 并添加这样的函数调用。
<select id = "numberlist" onchange="pickvalue(this.id)">
解决方案3
2 已采纳 2012-06-28 12:50:36
Try this Following...Mark it as answer if it helps you 尝试以下操作...如果有帮助，请将其标记为答案
<html>
<head>
<title>Title</title>
<script type="text/javascript" src="phonegap-1.4.1.js"> </script> <script type="text/javascript" src="JS/Util.js"></script>
<script type="text/javascript" src="JS/Language.js"></script>
<script type="text/javascript">
function dropdown()
{
var drp = document.getElementById("numberlist");
var optn = document.createElement("OPTION");
optn.text="3";
optn.value="3";
drp.add(optn);
}
</script>
</head>
<body onload="dropdown();">
<div id="main3">
</div>
<form>
<select id="numberlist" onchange="show()">
<option>12</option>
<option>24</option>
<option>36</option>
</select>
<script type="text/javascript">
function show() {
var e = document.getElementById('numberlist');
var txt = e.options[e.selectedIndex].text;
alert(txt);
}
</script>
</form>
</body>
</html>
解决方案4
1 2012-06-28 12:16:15
Here is a JQuery method: 这是一个JQuery方法：
$value = $("#numberlist option:selected").text();
alert($value);
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