使用javascript选择下拉菜单选项

Question

我有一个下拉菜单,我无法弄清楚如何制作一个javascript函数选择一个下拉菜单选项.我已经测试了变量的输出并且它们都是正确的,但是在单击时它仍然不会选择该选项.这是功能和下拉菜单.

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;
            }
        }
    }

菜单项

<select id="stateSelect" name="stateSelect">
    <option value="none">(None)</option>
    <option value="AL">Alabama</option>
    <option value="AK">Alaska</option>

Answer 1

更改以下行:

document.getElementById("stateSelect").selected = true;

至:

document.getElementById("stateSelect").selectedIndex = i;

Answer 2

Alt键.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;
            }
        }
...