Question

Say, I have two HTML elements – an input field and a button.

The code for both is generated programatically.

After I generate the code, I have a function that binds event handlers to those elements.

//Locate add to order button and bind event handler to it
this.input_add = document.getElementById("add_to_order");
this.input_add.onclick = 
    function () {
        return controller.addToOrder.call(controller);
    };

// Locate quantity input and bind event handler to it
this.input_quantity = document.getElementById("form_quantity");
this.input_quantity.onkeyup = 
    function () {
        return controller.changeQuantity.call(controller, this);
    };

Here’s the puzzle – controller.changeQuantity requires a reference to this.input_add.

As far as I can tell, I can’t pass this.input_add into the call parameter list for controller.changeQuantity.

I’ve found only one solution – putting a reference to this.input_add in the this.input_quantity object.

this.input_quantity.addButton = this.input_add

Are there any alternatives? Is this a good practice? I’m trying to keep my application as decoupled as possible.

Answer 1

Add your DOM objects to your “controller”, and set up your event handlers as part of that object, something like:

var controller = { ... };
controller.input_add = document.getElementById("add_to_order");
controller.input_quantity = document.getElementById("form_quantity");

controller.input_add.onclick = function() { controller.addToOrder.call(controller, this);}

Then you can reference these DOM elements from within your controller object at any point.

I often set up references to DOM elements, register event handlers, etc. in the setup code for my main Javascript controller object.