Backbone.js patch to prevent duplicate POSTs

gistfile1.js

// Queue of Backbone.Model save()s so that we don't issue multiple POSTs while waiting for
// the first one to come back. The first save() will always POST and the second will always PUT now.
// https://github.com/documentcloud/backbone/issues/345
// http://stackoverflow.com/a/6122530/137067
// https://gist.github.com/1037984
Backbone.Model.prototype._save = Backbone.Model.prototype.save;
Backbone.Model.prototype.save = function(attrs, options) {
    // Queue up consecutive requests if the model is new and the initial
    // POST request hasn't finished yet (xhr.readyState === 4 if the
    // "request finished and response is ready").
    if (this.isNew() && this.request && this.request.readyState !== 4) {

        var dit = this, args = arguments;
        // Passing an empty attrs value means that the model's current attributes should be persisted.
        // However in this case we're actually waiting until the previous POST has completed.
        // So we need to explicitly keep track of the attributes at the time of the original call,
        // or else by the time the promise callback completes, we might be trying to save some newly 
        // changed attributes (from the POST) which would make us lose our desired attributes from the 2nd save.
        if (_.isEmpty(attrs)) attrs = this.toJSON();
        $.when(this.request).always(function() {
            Backbone.Model.prototype._save.apply(dit, args);
        });
    } else {
        this.request = Backbone.Model.prototype._save.apply(this, arguments);
        return this.request;
    }
};