jquery plugin options array, preventing array overwrite

Question

I am writing a plugin for jquery, and I have used a code like this to allow users to specify options for the plugin:

var settings = $.extend({
    url     : 'error.json',
    slotWidth   : 100,
    slotHeight  : 100,
    gridWidth   : 6,
    gridHeight  : 3,
    basketLayers    : 1,
    layerDirection  : "vertical",
    classNames  : {
            productPanelParent  : '.products-panel-parent',
            productPanelTabs    : '.products-panel-tabs',
            productPanelGroup   : '.products-panel-container',
            productPanel    : '.products-panel',
            productBasketParent : '.products-basket-parent',
            productBasketGroup  : '.products-basket-container',
            productBasket   : '.products-basket',
            productBasketMenu   : '.products-basket-menu',
            basketSlot      : '.basket-slot',
            basketSlotFull  : '.basket-slot-full',
            basketSlotHelper    : '.basket-slot-highlight',
            product     : '.product',
            resetBasket     : '.clearBasket',
            resetLayer      : '.clearLayer',
            viewLayer       : '.viewLayer'
          }
}, options);

The problem is that when I try to override one of the classNames, the whole array is written over with null values wherever a property wasn't specificed.

So for example, I'll do something like this:

$('#somediv').myPlugin({
    gridWidth : 4,
    gridHeight : 2,
    classNames : {
        productBasket : '.small_basket'
    }
});

And the settings.classNames.productBasket property will be the correct value, but everything is in settings.classNames will be null.

How do I get around this?
(without writing a custom function to handle default values in the array?)

Answer 1

The first argument to jQuery.extend() can be a boolean. If it's true , then the extension is "deep" (the merge is made recursively):

var settings = $.extend(true, defaults, options);

From the docs:

The merge performed by $.extend() is not recursive by default; if a property of the first object is itself an object or array, it will be completely overwritten by a property with the same key in the second object. The values are not merged... However, by passing true for the first function argument, objects will be recursively merged .