localeCompare array with null values

Question

When I'm sorting my array I get the following error in console:

Uncaught TypeError: Cannot read property 'localeCompare' of null

What I've tried so far:

HTML:

<table class="table table table-striped table-bordered table-hover" id="userLastSyncTable">
<thead>
    <tr>
        <th class="sortable sortDevicePlatform orderDevicePlatformByASC">Device Platform</th>
    </tr>
</thead>
<tbody></tbody>

JavaScript/JQuery:

var TestArray = ["iOS 7", null, "iOS 8.4", null, null, null, "iOS 9"];

ShowUserSyncTable();

function ShowUserSyncTable() {
    var tableRecord = '';

    // Loop through all the returned records and add them to select box
    for (var i = 0; i < TestArray.length; i++) {
        tableRecord += "<tr id=" + "" + "><td>" + TestArray[i] + "</td></tr>";

    }

    $('#userLastSyncTable').find('tbody').html(tableRecord);
}

$(".sortDevicePlatform").click(function () {

    var clickedDevicePlatformSorting = $(this).hasClass('orderDevicePlatformByASC') ? 'orderDevicePlatformByDESC' : 'orderDevicePlatformByASC';

                $('.sortDevicePlatform').removeClass('orderDevicePlatformByASC').removeClass('orderDevicePlatformByDESC');
            $('.sortDevicePlatform').addClass(clickedDevicePlatformSorting);
    // Sort the sync list based on device platform
    TestArray.sort(function (a, b) {

        if (!a) {
            // Change this values if you want to put `null` values at the end of the array
            return -1;
        }
        if (!b) {
            // Change this values if you want to put `null` values at the end of the array
            return +1;
        }

        if (clickedDevicePlatformSorting == 'orderDevicePlatformByASC' && a) return a && b ? a.localeCompare(b) : -1;
        else if (b) return a && b ? b.localeCompare(a) : 1;
    });

    ShowUserSyncTable();
});

How do I go about sorting the array with null values?

Update Fiddle for testing:

FIDDLE

Expected out come:

One click show:

iOS 7, iOS 8.4, iOS 9, null, null, null, null

Another click show:

iOS 9, iOS 8.4, iOS 7, null, null, null, null

Answer 1

You cannot call a function on null. You have some null values in your array. So when you try to sort these values, it crashes.

You can protect your code to avoid that.

TestArray.sort(function(a, b) {
    if (!a) {
       // Change this values if you want to put `null` values at the end of the array
       return -1;
    }

    if (!b) {
       // Change this values if you want to put `null` values at the end of the array
       return +1;
    }

    if (sorted)
        return a.localeCompare(b);
    else
        return b.localeCompare(a);
});

But in my opinion, you should get rid of this null values in the array. You can filter them :

TestArray = TestArray.filter(function(val) {
    return val != null;
});

Answer 2

Try this: Demo.

Remove orderDevicePlatformByASC class name from clickable <th ...>. Because, its initial appearance is not sorted. Use this for sorting.

TestArray.sort(function (a, b) {
     if (clickedDevicePlatformSorting == 'orderDevicePlatformByASC' && a)            
        return  b ? a.localeCompare(b) : -1;
     else if (b) 
        return a ? b.localeCompare(a) : 1;
});