Question

I have a plugin like this:

(function($){
  $.fn.extend({
    myplugin: function () {
      var jobs = [];
      this.each(function(){
        jobs.push($(this).one(
          'load',
          function(){
            // Line A: "Load" fires here
            // Replace image source
            $(this).attr('src','new_url');
            // Line B: Everything is done, fire now!
          }));
        });
        // Callback
        $.when.apply(null,jobs).then(function(){
          alert($(this).attr('src'));
        });
        return this;
      }
    });
  })(jQuery);

The when helper always alerts old image source. Because it is being called after load on Line A. But I need to fire it on Line B.

How to solve this? Any ideas?

Thank you!

Answer 1

You’re not passing any deferreds to when. All you’re passing it is an array of jQuery objects.

Create a new deferred for every item in the collection, then resolve it within the event listener:

(function($){
    $.fn.myplugin = function () {
        var deferreds = [];

        this.each(function() {
            var deferred = $.Deferred();

            deferreds.push(deferred);

            $(this).one('load', function() {
                this.src = 'new_url';
                deferred.resolve();
            });
        });

        $.when.apply($, deferreds).then(function() {
            alert('All sources have been changed.');
        });

        return this;
    };
})(jQuery);

---

To be more concise, you can pass a function to the deferred constructor instead:

this.each(function (i, element) {
    deferreds.push( $.Deferred(function (deferred) {

        $(element).one('load', function() {
            this.src = 'new_url';
            deferred.resolve();
        });

    }));
});