How to show <Select > in sorted order

Question

How can I sort the <option> elements of a <select> tag using JavaScript?

Here is the HTML I have:

<form action="example.asp">
<div>
<select size="3">
<option value="op2" >Option 2</option>
<option value="op1">Option 1</option>
<option value="op4">Option 4</option>
<option value="op3">Option 3</option>

</select>
</div>
</form> 

Answer 1

If the value is different than the text, use the following function to sort both of them. This is just an updated version of above solution and will keep both the name and associated value.

<script language="JavaScript" type="text/javascript">
function sortList() 
{ 
    var lb = document.getElementById('mylist'); 
    arrTexts = new Array(); 
    arrValues = new Array(); 
    arrOldTexts = new Array(); 

    for(i=0; i<lb.length; i++) 
    { 
        arrTexts[i] = lb.options[i].text; 
        arrValues[i] = lb.options[i].value; 
        arrOldTexts[i] = lb.options[i].text; 
    } 

    arrTexts.sort(); 

    for(i=0; i<lb.length; i++) 
    { 
        lb.options[i].text = arrTexts[i]; 
        for(j=0; j<lb.length; j++) 
        { 
            if (arrTexts[i] == arrOldTexts[j]) 
            { 
                lb.options[i].value = arrValues[j]; 
                j = lb.length; 
            } 
        } 
    } 
}
</script>

Answer 2

<script language="JavaScript" type="text/javascript">
function sortlist() {
var lb = document.getElementById('mylist');
arrTexts = new Array();

for(i=0; i<lb.length; i++)  {
  arrTexts[i] = lb.options[i].text;
}

arrTexts.sort();

for(i=0; i<lb.length; i++)  {
  lb.options[i].text = arrTexts[i];
  lb.options[i].value = arrTexts[i];
}
}
</script>


<form action="#">
<select name=mylist id=mylist size=5>
<option value="Anton">Anton
<option value="Mike">Mike
<option value="Peter">Peter
<option value="Bill">Bill
<option value="Carl">Carl
</select>
<br>
<a href="javascript:sortlist()">sort</a>
</form>