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问题:

UPDATE: Code has been updated per Dan's comments.

I have a problem with a project I'm working on. I need to create a list of checkboxes depending on what is selected in a select dropdown above. I would like to use javascript for this. I was able to create a select dropdown dependent on the select above but the client wants checkboxes instead. I figured it would be essentially done the same way, except making checkboxes this time, but I can't get it to work. I usually use php for my programing and therefore don't know javascript too well. Here is the code I have to make the select dropdown.... what would be the best way to make it a list of checkboxes instead? Please note that this code has been greatly reduced to keep it easy to read (only the parts that matter are here).

Code:

<!DOCTYPE html>
<html>
<head>
<script type="text/javascript">
    function populate(slct1,slct2){
var s1 = document.getElementById(slct1);
var s2 = document.getElementById(slct2);
s2.innerHTML = "";
if(s1.value == "Cat1"){
    var optionArray = ["Subcat1","Subcat1.1","Subcat1.2"];
} else if(s1.value == "Cat2"){
    var optionArray = ["Subcat2","Subcat2.1","Subcat2.2"];
} else if(s1.value == "Cat3"){
    var optionArray = ["Subcat3","Subcat3.1","Subcat3.3"];
}
for(var option in optionArray){
     if (optionArray.hasOwnProperty(option)) {
        var pair = optionArray[option];
        var newOption = document.createElement("option");
        newOption.value = pair;
        newOption.innerHTML = pair;
        s2.options.add(newOption);
    }
}
}
</script>
</head>
<body>
<h2>Dynamic Select Dropdown</h2>
<hr />
Choose a Category:
<select id="slct1" name="slct1" onchange="populate(this.id,'slct2')">
   <option value=""></option>
   <option value="Cat1">Cat1</option>
   <option value="Cat2">Cat2</option>
   <option value="Cat3">Cat3</option>
</select>
<hr />
   Choose Subcategory:
<select id="slct2" name="slct2"></select>
<hr />
</body>
</html>

Any help would be greatly appreciated and I would try my best to repay the favor if you ever needed help with any development.

回答1:

A checkbox is a simple input element with type='checkbox'. So you have to prepare at least two things: a text node for the description of the box and the box itself. In this case it's also good to use a <label> element to include both things mention before:

// create the necessary elements
var label= document.createElement("label");
var description = document.createTextNode(pair);
var checkbox = document.createElement("input");

checkbox.type = "checkbox";    // make the element a checkbox
checkbox.name = "slct[]";      // give it a name we can check on the server side
checkbox.value = pair;         // make its value "pair"

label.appendChild(checkbox);   // add the box to the element
label.appendChild(description);// add the description to the element

// add the label element to your div
document.getElementById('some_div').appendChild(label);

You have to do the steps above for every pair. Note that you have to clear the given <div id="some_div"></div> before you populate it:

// clear the former content of a given <div id="some_div"></div>
document.getElementById('some_div').innerHTML = '';

回答2:

The process of creating a checkbox dynamically is indeed a little more involved than creating a select option. You need to create:

the checkbox
its label
and possibly a <br> for styling

Here's the gist of the code, with the full fiddle at http://jsfiddle.net/dandv/9aZQF/2/:

for (var option in optionArray) {
    if (optionArray.hasOwnProperty(option)) {
        var pair = optionArray[option];
        var checkbox = document.createElement("input");
        checkbox.type = "checkbox";
        checkbox.name = pair;
        checkbox.value = pair;
        s2.appendChild(checkbox);

        var label = document.createElement('label')
        label.htmlFor = pair;
        label.appendChild(document.createTextNode(pair));

        s2.appendChild(label);
        s2.appendChild(document.createElement("br"));    
    }
}