how to toggle attr() in jquery

Solution 1:

If you're feeling fancy:

$('.list-sort').attr('colspan', function(index, attr){
    return attr == 6 ? null : 6;
});

Working Fiddle

_{ES6 Syntax (2021):}

$('.list-sort').attr('colspan', (_, attr) => attr == 6 ? null : 6));

Solution 2:

$('.list-toggle').click(function() {
    var $listSort = $('.list-sort');
    if ($listSort.attr('colspan')) {
        $listSort.removeAttr('colspan');
    } else {
        $listSort.attr('colspan', 6);
    }
});

Here's a working fiddle example.

See the answer by @RienNeVaPlus below for a more elegant solution.

Solution 3:

For readonly/disabled and other attributes with true/false values

$(':submit').attr('disabled', function(_, attr){ return !attr});