Javascript 如何在javascript中的下拉列表中获取值的索引？
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how to get the index of value in drop down in javascript?
提问by Red Swan
I have dropdown list on my aspx page. I want to mannually set the selected value which in exist in the dropdown list. this value i am getting in var. i want to set this value as selected value when page get initialize. I want this in javascript. is there any property for dropdown as ddp.SelectedValue='40'..? here I don't know the index of 40 in the list.
我的 aspx 页面上有下拉列表。我想手动设置下拉列表中存在的选定值。我在 var 中得到的这个值。我想在页面初始化时将此值设置为选定值。我想要这个在 javascript 中。是否有任何下拉属性为 ddp.SelectedValue='40'..？这里我不知道列表中 40 的索引。
回答by Mike Samuel
selectedIndexis a property of HTMLSelectElement so you can do the following:
selectedIndex是 HTMLSelectElement 的属性，因此您可以执行以下操作：
<select id="foo"><option>Zero<option>One<option>Two</select>
<script>
document.getElementById('foo').selectedIndex = 1; // Selects option "One"
</script>
And given an OPTION element, you can get its index using the indexproperty:
给定一个 OPTION 元素，您可以使用以下index属性获取其索引：
<select><option>Zero<option id="bar">One<option>Two</select>
<script>
alert(document.getElementById('bar').index); // alerts "1"
</script>
回答by bobince
I want to manually set the selected value
我想手动设置选定的值
Iterate the select's options list to get the optionyou were interested in and set selectedon it:
迭代select的选项列表以获取option您感兴趣的选项并对其进行设置selected：
var options= document.getElementById('ddp').options;
for (var i= 0; n= options.length; i<n; i++) {
if (options[i].value==='40') {
options[i].selected= true;
break;
}
}
this will select the first option with a matching value. If you have more than one option with the same value, or a multiple-select, you may need different logic.
这将选择具有匹配值的第一个选项。如果您有多个具有相同值的选项或多项选择，则可能需要不同的逻辑。
This:
这个：
document.getElementById('ddp').value= '40';
is specified by HTML5 to do the same, and has worked in most modern browsers for ages, but still fails in IE, unfortunately (even IE9).
由 HTML5 指定做同样的事情，并且已经在大多数现代浏览器中工作了很长时间，但不幸的是，在 IE 中仍然失败（甚至 IE9）。
回答by Swathi
<script type="text/javascript" src="http://ajax.aspnetcdn.com/ajax/jQuery/jquery 1.6.2.min.js" />
<script language="JavaScript">
$(function() {
quickSelect();
// Handler for .ready() called.
});
function quickSelect() {
var bnd = "40";
if (bnd != "") {
$("#ddp option[value='" + bnd + "']").attr("selected", "selected");
}
}
</script>
