How do I delete a callback deferred.progress?

Question

How do I delete a previously assigned handler?

var deferred = $.Deferred();

var callback = function(n) {
    console.log('Test ' +n);
}

deferred.progress(callback);

deferred.notify(1);

$(deferred).off('progress', callback); // It doesn't work =(

deferred.notify(2);

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>

Is there a way built into jQuery to remove jQuery.Deferred handlers?

Answer 1

I found out that jQuery.Deferred uses jQuery.Callbacks. This allowed us to write a wrapper for jQuery.Deferred and pull the ability to manage handlers to the top. Below is an example.

(function() {
    
    var deferred_original = jQuery.Deferred;
    
    jQuery.Deferred = function() {
        
        var callbacks = [];
        
        var callbacks_original = jQuery.Callbacks;
        
        jQuery.Callbacks = function() {
            var callback = callbacks_original.apply(this, arguments);
            callbacks.push(callback);
            return callback;
        }
        
        var deferred = deferred_original.apply(this, arguments);
        deferred.callbacks = jQuery(callbacks);
        
        jQuery.Callbacks = callbacks_original;
        
        return deferred;
        
    }
    
})();

// Test:

var deferred = $.Deferred();

var callback = function(n) {
    console.log('Test ' +n);
}

deferred.progress(callback);

deferred.notify(1);

// This will remove the progress handler:
deferred.callbacks.each(function(n, c) { c.remove(callback); });

deferred.notify(2);

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>

Answer 2

No, there's no function to remove already-registered callbacks on a $.Deferred().