Question

Why doesn’t my jQuery code add and later remove loading class?

$('#crop').click(function (ev) {
    ev.preventDefault()
    $.post('frame.php?action=crop', dimensions, function (json) {
        $('body').addClass('loading')
        picture()
    }, 'json')
    $('body').removeClass('loading')
})

Chrome and Firebug consoles are empty, so there shouldn’t be any errors.
jQuery version is 1.4.4

Answer 1

What it does is remove and then later add the class.

You’re adding the class in the callback to $.post(), which will happen long after the subsequent removal of the class. If you swap those lines (do the add after the $.post() call and the remove in the callback) then it’ll be closer to what you want.