Javascript 使用javascript选择下拉菜单选项
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Select dropdown menu option with javascript
提问by shinjuo
I have a dropdown menu and I cannot figure out how to make a javascript function select a drop down menu option. I have tested the output of the variables and they are all correct, but it still will not select the option when clicked. Here is the function and drop down menu.
我有一个下拉菜单，但我不知道如何让 javascript 函数选择一个下拉菜单选项。我已经测试了变量的输出，它们都是正确的，但是单击时仍然不会选择该选项。这是功能和下拉菜单。
Function
功能
function formFill(a, b, c){
theform.from.value = a;
theform.to.value = b;
for(var i = 0;i < document.getElementById("stateSelect").length;i++){
if(document.getElementById("stateSelect").options[i].value == c ){
document.getElementById("stateSelect").selected = true;
}
}
}
Menu item
菜单项
<select id="stateSelect" name="stateSelect">
<option value="none">(None)</option>
<option value="AL">Alabama</option>
<option value="AK">Alaska</option>
回答by David Hancock
Change the line that reads:
更改读取的行：
document.getElementById("stateSelect").selected = true;
document.getElementById("stateSelect").selected = true;
to:
到：
document.getElementById("stateSelect").selectedIndex = i;
document.getElementById("stateSelect").selectedIndex = i;
回答by Anatoly Mironov
Alt. you can set selected to the actual option: select.options[i].selected = true;
替代。您可以将 selected 设置为实际选项：select.options[i].selected = true;
...
var select = document.getElementById("stateSelect");
for(var i = 0;i < select.options.length;i++){
if(select.options[i].value == c ){
select.options[i].selected = true;
}
}
...
