You could replace the original jQuery addClass and removeClass functions with your own that would call the original functions and then trigger a custom event. (Using a self-invoking anonymous function to contain the original function reference)
(function( func ) {
$.fn.addClass = function() { // replace the existing function on $.fn
func.apply( this, arguments ); // invoke the original function
this.trigger('classChanged'); // trigger the custom event
return this; // retain jQuery chainability
}
})($.fn.addClass); // pass the original function as an argument
(function( func ) {
$.fn.removeClass = function() {
func.apply( this, arguments );
this.trigger('classChanged');
return this;
}
})($.fn.removeClass);
Then the rest of your code would be as simple as you'd expect.
$(selector).on('classChanged', function(){ /*...*/ });
Update:
This approach does make the assumption that the classes will only be changed via the jQuery addClass and removeClass methods. If classes are modified in other ways (such as direct manipulation of the class attribute through the DOM element) use of something like MutationObserver
s as explained in the accepted answer here would be necessary.
Also as a couple improvements to these methods:
classAdded
) or removed (classRemoved
) with the specific class passed as an argument to the callback function and only triggered if the particular class was actually added (not present previously) or removed (was present previously)Only trigger classChanged
if any classes are actually changed
(function( func ) {
$.fn.addClass = function(n) { // replace the existing function on $.fn
this.each(function(i) { // for each element in the collection
var $this = $(this); // 'this' is DOM element in this context
var prevClasses = this.getAttribute('class'); // note its original classes
var classNames = $.isFunction(n) ? n(i, prevClasses) : n.toString(); // retain function-type argument support
$.each(classNames.split(/\s+/), function(index, className) { // allow for multiple classes being added
if( !$this.hasClass(className) ) { // only when the class is not already present
func.call( $this, className ); // invoke the original function to add the class
$this.trigger('classAdded', className); // trigger a classAdded event
}
});
prevClasses != this.getAttribute('class') && $this.trigger('classChanged'); // trigger the classChanged event
});
return this; // retain jQuery chainability
}
})($.fn.addClass); // pass the original function as an argument
(function( func ) {
$.fn.removeClass = function(n) {
this.each(function(i) {
var $this = $(this);
var prevClasses = this.getAttribute('class');
var classNames = $.isFunction(n) ? n(i, prevClasses) : n.toString();
$.each(classNames.split(/\s+/), function(index, className) {
if( $this.hasClass(className) ) {
func.call( $this, className );
$this.trigger('classRemoved', className);
}
});
prevClasses != this.getAttribute('class') && $this.trigger('classChanged');
});
return this;
}
})($.fn.removeClass);
With these replacement functions you can then handle any class changed via classChanged or specific classes being added or removed by checking the argument to the callback function:
$(document).on('classAdded', '#myElement', function(event, className) {
if(className == "something") { /* do something */ }
});