Question

我试着寻找一段时间的答案，但无济于事。

我正在尝试做一个简单的在线计算器（计算一些光伏面板能量），但我陷入了一些简单的事情（虽然我使用Flash的ActionScript 3.0已经有一段时间了，但我是Javascript的新手。） / p>

我需要做的是一个html选择，它定义了页面中出现的其他选择组。这样的事情（显然这不起作用，只是举个例子）：

HTML

<html>
<body>
<select id="test1" onclick="checkField()">
<option>Selected A Group</option>
<option>Selected B Group</option>
</select>
<script>//insert second group here</script>
</body>
</html>

的Javascript

function checkField(){
var temp = document.getElementById('test1').value;

if(temp === "Selected A Group"){
//insert code to "echo" the first optional select group
} else {
//insert code to "echo" the second optional select group
}
}

很抱歉，如果它有点令人困惑，但我真的无法解释这一切。以下是我想要的示例，选择一个选项会使其他字段相应更改：http://www.toshiba.eu/innovation/download_drivers_bios.jsp

Answer 1

你几乎就在那里，实际上javascript没有直接“回显”值，它使用console.log(your value);将值记录到调试控制台，类似于AS2 trace()如果我的内存没有失败。

要将信息“输出”到文档，您应该查看document.write 当你使用document.write时，它将直接写入文件结尾。

“正确”的方法是创建一个DOM元素，在其中包含您想要的元素，然后将其附加到所需的元素。看一下评论

<!-- Be Aware to use the onchange trigger on select boxes, if you use onclick the function will run, even
if you didn't really chose any option -->
<select id="test1" onchange="checkField()">
<!-- Is good to have a first non-value option, better to trigger the onchange event, if you have 
Select A Group as first option and you click on it, it didn't really "Change", you would have to
pick B Group and then A Group again to trigger the onchange event correctly. -->
<option value="">-- select an option --</option>
<!-- You can have a value attribute on the options, so it's easy to process when programming
while displaying a more detailed description to the users -->
<option value="A">Selected A Group</option>
<option value="B">Selected B Group</option>
</select>

<!-- We create an empty element where we are gonna place the new Select -->
<div id="newSelect"></div>

<!-- By Placing the Javascript on the end of <body>, we ensure that all the DOM elements loaded before running the script -->
<script>
    function checkField(){
        var newSelect = document.getElementById('newSelect'); //targeting container;    
        var temp = document.getElementById('test1').value;

        //Some tasks we do always the option chose is not the first custom one, so we don't have to repeat it
        //on the two If's below
        if(temp !== ""){
            // We remove the select if we placed one already before, so we can add the new one,
            // For example if we chose B Group but changed our mind and Chose A Group later.
            if(oldChild = newSelect.getElementsByTagName('select')[0]){
                oldChild.remove();
            }

            var select = document.createElement("select");
            select.setAttribute('id', 'newSelect');

        }

        if(temp === "A"){
            //you could do JUST:
            //body.innerHTML = "all the html you want in here" instead of all the code following;
            //but all those code is supposed to be the "correct way" of adding elements to the HTML,
            //Google a bit about that for detailed explanations

            var option1 = document.createElement("option");
            option1.value = 1;
            option1.text = "Option 1";
            var option2 = document.createElement("option");
            option1.value = 2;
            option2.text = "Option 2";

            select.appendChild(option1);
            select.appendChild(option2);

            newSelect.appendChild(select);
        } else {
            var option1 = document.createElement("option");
            option1.value = 3;
            option1.text = "Option 3";
            var option2 = document.createElement("option");
            option1.value = 4;
            option2.text = "Option 4";

            select.appendChild(option1);
            select.appendChild(option2);

            newSelect.appendChild(select);
        }
    }
</script>

当然有一些方法可以使这个稍微缩短，如果您的数据输出有一个模式，使用循环，但让我们以“简单”的方式做到这一点，以便您掌握Javascript。

希望这一切对你有所帮助!!

Answer 2

以下是演示http://codepen.io/anon/pen/izAHo 你做得差不多。

您应该将onclick事件放在选项标记上，以根据所选的选项触发更改。

<强> HTML

<html>
<body>

<select id="test1">
<option onclick="checkField()">Selected A Group</option>
<option>Selected B Group</option>
</select>

<select id="test2">
<option  onclick="check2Field()">Selected C Group</option>
<option>Selected D Group</option>
</select>

<script>//insert second group here</script>
</body>
</html>

<强> JS

function checkField(){
var temp = document.getElementById('test1').value;
if(temp === "Selected A Group"){
document.getElementById('test2').innerHTML="<option>Selected halloooo Group</option>";
} else {
//insert code to "echo" the second optional select group
}
}

查看我的演示以获得更清晰的信息。

Answer 3

在这里演示： http://jsfiddle.net/3GkrX/

与Mevins差不多......改为切换/案例

HTML：

<select id="test1" id="name" onchange="checkField()">
    <option>----</option>
<option>Selected A Group</option>
<option>Selected B Group</option>
</select>
<div id="optional">Please select!</div>

JS：

function checkField(){
var temp = document.getElementById('test1').value;

    switch(temp){

        case "Selected A Group":
            document.getElementById("optional").innerHTML="<select name='optionalA'><option>1</option><option>2</option></select>";
            break;
        case "Selected B Group":
            document.getElementById("optional").innerHTML="<select name='optionalB'><option>3</option><option>4</option></select>";
            break
            default:
                document.getElementById("optional").innerHTML="Please select!";
            break;

    }

}

还将第二组添加为实际选项，默认为“请选择”。在您的情况下可能需要也可能不需要

Javascript多个选择框

3 个答案: