Sorting dropdown list using Javascript

You could use jQuery and something like this:

$("#id").html($("#id option").sort(function (a, b) {
    return a.text == b.text ? 0 : a.text < b.text ? -1 : 1
}))

But it's probably better to ask why and what you're trying to accomplish.

<select id="foo" size="10">
  <option value="3">three</option>
  <option value="1">one</option>
  <option value="0">zero</option>
  <option value="2">two</option>
</select>
<script>
  // WARN: won't handle OPTGROUPs!
  var sel = document.getElementById('foo');
  // convert OPTIONs NodeList to an Array
  // - keep in mind that we're using the original OPTION objects
  var ary = (function(nl) {
    var a = [];
    for (var i = 0, len = nl.length; i < len; i++)
      a.push(nl.item(i));
    return a;
  })(sel.options);
  // sort OPTIONs Array
  ary.sort(function(a,b){
    // sort by "value"? (numeric comparison)
    // NOTE: please remember what ".value" means for OPTION objects
    return a.value - b.value;
    // or by "label"? (lexicographic comparison) - case sensitive
    //return a.text < b.text ? -1 : a.text > b.text ? 1 : 0;
    // or by "label"? (lexicographic comparison) - case insensitive
    //var aText = a.text.toLowerCase();
    //var bText = b.text.toLowerCase();
    //return aText < bText ? -1 : aText > bText ? 1 : 0;
  });
  // remove all OPTIONs from SELECT (don't worry, the original
  // OPTION objects are still referenced in "ary") ;-)
  for (var i = 0, len = ary.length; i < len; i++)
    sel.remove(ary[i].index);
  // (re)add re-ordered OPTIONs to SELECT
  for (var i = 0, len = ary.length; i < len; i++)
    sel.add(ary[i], null);
</script>

You can try JQuery sort function for this work --

Try this

HTML CODE -

<select id="ddlList">
  <option value="3">Three</option>
  <option value="1">One</option>
  <option value="1">one</option>
  <option value="1">a</option>
  <option value="1">b</option>
  <option value="1">A</option>
  <option value="1">B</option>
  <option value="0">Zero</option>
  <option value="2">Two</option>
  <option value="8">Eight</option>
</select>

JQUERY CODE -

$("#ddlList").html($('#ddlList option').sort(function(x, y) {        
     return $(x).text().toUpperCase() < $(y).text().toUpperCase() ? -1 : 1;
}));
$("#ddlList").get(0).selectedIndex = 0;
e.preventDefault();

OR

you can also use array sorting for this -

Try This

 var options = $('#ddlList option');
 var arr = options.map(function (_, o) { return { t: $(o).text(), v: o.value }; }).get();
 arr.sort(function (o1, o2) { return o1.t.toUpperCase() > o2.t.toUpperCase() ? 1 : o1.t.toUpperCase() < o2.t.toUpperCase() ? -1 : 0; });         
 options.each(function (i, o) {
     o.value = arr[i].v;
     $(o).text(arr[i].t);
 });

Put the option values and text into an array, sort the array, then replace the existing option elements with new elements constructed from the sorted array.

DEPENDS ON JQUERY

function SortOptions(id) {
    var prePrepend = "#";
    if (id.match("^#") == "#") prePrepend = "";
    $(prePrepend + id).html($(prePrepend + id + " option").sort(
        function (a, b) { return a.text == b.text ? 0 : a.text < b.text ? -1 : 1 })
    );
}

Examples:

<select id="my-list-id"> is sorted with:

SortOptions("#my-list-id");

OR

SortOptions("my-list-id");

FOR DROPDOWN FOR WHOLE PROJECT

$(document).ready(function () {
    $.when($('select').addClass('auto-drop-sort')).then($.fn.sortDropOptions("auto-drop-sort"))
})

/*sort all dropdown*/
$.fn.sortDropOptions = function(dropdown_class){
    var prePrepend = ".";
    if (dropdown_class.match("^.") == ".") prePrepend = "";
    var myParent = $(prePrepend + dropdown_class);
    $.each(myParent, function(index, val) {
        /*if any select tag has this class 'manual-drop-sort' this function wont work for that particular*/
        if ( ! $(val).hasClass('manual-drop-sort') ) {
            var selectedVal = $(val).val()
            $(val).html($(val).find('option').sort(
                function (a, b) {
                    if ( a.value != -1 && a.value != 0 && a.value != '' ) {
                        return a.text == b.text ? 0 : a.text < b.text ? -1 : 1 
                    }
                })
            );
            $(val).val(selectedVal)
        }else{
            /* set custom sort for individual select tag using name/id */
        }
    });
}

The answers provided didn't really suit my case so I made my own (especially not wanting jQuery). Figured it might help others.

sortDropDown(document.querySelector('select'));

function sortDropDown(d){
    //save option values
    var existingOptions=d.options; 

    //keep track of previously selected option
    var selectedOpt=d.selectedOptions[0].value;

    //turn nodeList into Array of values
    existingOptions=[].slice.call(existingOptions).map(function(a){return a.innerText});

    //make sure options are unique
    existingOptions = existingOptions.filter( function(value, index, self) { 
        return self.indexOf(value) === index;
    }); 

    //sort options
    existingOptions.sort();

    //keep "All" option as first element
    existingOptions.splice(0, 0, existingOptions.splice(existingOptions.indexOf('All'), 1)[0]);

    //repleace dropdown contents
    var t='';
    existingOptions.forEach(function(a){
        t+='<option '+(a==selectedOpt?'selected':'')+' value="'+a+'">'+a+'</option>';
    });
    d.innerHTML=t;
}

Here is a way you could do it after the fact... But really it would be better to sort the array first, then fill it. If you MUST do it afterward, here... You can also throw in ignore case if you want. You could also not store in sortedOptionsAll and go directly to filling the combo. Your choice. It can be refactored, simplified, etc. This is a general idea though.

<script>
    function sortCombo(comboBoxId) {
    //get drop down
    let comboBox = document.getElementById(comboBoxId);

    //create array for storage 
    let optionsText = [];
    let optionsTextSorted = [];
    let optionsValues = [];
    let sortedOptionsAll = [];

    //store in the array 
    Array.from(comboBox.options).forEach(x => {
        optionsText.push(x.text);
        optionsValues.push(x.value);
    }
    );

    optionsTextSorted = [...optionsText];
    optionsTextSorted.sort();
    optionsTextSorted.forEach(x => {
        sortedOptionsAll.push({ value: optionsValues[optionsText.indexOf(x)], text: x });
    }
    );

    //clear the combo box 
    Array.from(comboBox.options).forEach(x => x.text = '');

    //fill the combobox 
    for (let i = 0; i < sortedOptionsAll.length; i++) {
        document.getElementById(comboBoxId)[i].text = sortedOptionsAll[i].text;
        document.getElementById(comboBoxId)[i].value = sortedOptionsAll[i].value;
    }
}
</script>