Javascript multiple select boxes

Javascript multiple select boxes

本文关键字：boxes select multiple Javascript      更新时间：2023-09-26

我尝试寻找这个问题的答案一段时间，但无济于事。

我

正在尝试做一个简单的在线计算器（计算一些光伏板的能量），但我被困在简单的东西上（我是Javascript的新手，尽管我使用Flash的ActionScript 3.0一段时间）。

我需要做的是一个 html 选择，用于定义页面中出现的其他选择组。像这样的东西（显然这不起作用，只是树立一个例子）：

.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>

爪哇语

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
}
}

对不起，如果它有点令人困惑，但我不能很好地解释这一切。以下是我想要的示例，选择一个选项会使其他字段相应地更改：http://www.toshiba.eu/innovation/download_drivers_bios.jsp

你快到了，实际上 JavaScript 不会直接"回显"值，它会使用console.log(your value);将值记录到调试控制台，类似于 AS2 trace()如果我的内存没有出现故障。

要将信息"输出"到文档中，您应该查看 document.write当你使用document.write时，它将直接写入文档端。

"正确"的方法是创建一个 DOM 元素，其中包含您想要的元素，然后将其附加到所需的元素。看看评论

<!-- 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，有一些方法可以稍微缩短一点，如果你的数据输出有模式，请使用循环，但让我们用"简单"的方式去做，这样你就可以掌握Javascript。

希望这一切都对你有所帮助！！

演示在这里：http://jsfiddle.net/3GkrX/

和梅文斯差不多。虽然改为开关/外壳

.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;
    }
}

还添加了第二组作为实际选项，并将默认值添加为"请选择"。 在您的情况下可能是必需的，也可能不是必需的

这是演示 http://codepen.io/anon/pen/izAHo你做得几乎是对的。

您应该将 onclick 事件放在选项标记上，以根据所选选项触发更改。

.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>

.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。

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