javascript 获取下拉列表的选定值
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Get the selected value of a dropdown list
提问by harsh
I have the follwing code. 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(). I need to use alert() from within the < body > of the html. Is that possible?
我有以下代码。我想在用户更改下拉列表的选定值后获取它的值，或者让 alert() 显示默认值。我需要在 html 的 < body > 中使用 alert()。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>
回答by 0x499602D2
Use the code:
使用代码：
selectElement.options[ selectElement.options.selectedIndex ];
to find the index that is selected.
找到被选中的索引。
So where you say var drp = document.getElementById("numberlist");you can now find the value of the index by doing:
所以你说var drp = document.getElementById("numberlist");你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 onchangeevent so that whenever you change the selectedIndexof the element, you will be able to obtain it's value:
将代码添加到onchange事件中，这样无论何时更改selectedIndex元素的 ，您都可以获取它的值：
Here is a DEMO
这是一个演示
回答by Muhammad Saifuddin
add this function within script tag.
在脚本标签中添加此功能。
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)">
回答by himadri
Try this Following...Mark it as answer if it helps you
试试这个以下...如果它对你有帮助，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>
回答by Danny
Here is a JQuery method:
这是一个 JQuery 方法：
$value = $("#numberlist option:selected").text();
alert($value);
