How to extend "onAdd" method (for Leaflet-draw)?

[ahalota]

I'm trying to extend the Leaflet-draw plugin to include two extra buttons. 

I do not need to make changes to initialize(), which offers the addInitHook() function, but I do want to make a change to onAdd(), which is where Leaflet-draw creates its toolbar.

Is there something such as addInitHook(), but for other methods? I have tried redefining the onAdd() function, but then don't know how to access the original one in order to run all of those things first.

My solution now has created a subclass and simply extends() the L.Control.Draw class, but I really would prefer to have it simply add functionality to the regular onAdd() instead of forcing creating of a new class. This is because I have several extensions I am writing and I'd like each to be able to stand-alone update the L.Control.Draw without having to use a new class name (so if I add a button in Extension A, I can later use Extension B to add a second button without them having to know about each other).

Here's a snippet of the code I have right now. It works, but isn't quite what I want:

L.Control.DrawPlus = L.Control.Draw.extend({

initialize: function(options) {

        L.setOptions(this, options);

        

        L.Control.Draw.prototype.initialize.call(this, options);

    },

    

onAdd: function(map) {

var container = L.Control.Draw.prototype.onAdd.call(this,map);

var drawContainer = container.getElementsByClassName('leaflet-draw-toolbar-top')[0];

if (this.options.draw.shapefile == true){

this._addShapefileButton(drawContainer);

}

        return container;

    },

       _addShapeFileButton: function(drawContainer) { /*code to add div to toolbar*/ }
});