Question

jQuery has a very neat extend method, which merges 2 objects into one.

On the jQuery Plugins authoring page they show an example as follows:

var settings = $.extend({
    'location'         : 'top',
    'background-color' : 'blue'
}, options);

However, I’ve seen many plugins pass an empty object as the first parameter, like so:

var settings = $.extend({}, {
    'location'         : 'top',
    'background-color' : 'blue'
}, options);

As far as I can tell, these two do the exact same thing. The only difference would be if the defaults would have been stored in its own variable:

var defaults = {
    'location'         : 'top',
    'background-color' : 'blue'
},
settings = $.extend({}, defaults, options);

This way, you can always access your defaults without them being overridden by the options.

---

Here’s the question: Why do so many plugin authors opt to pass an empty object to extend, even when they don’t store the defaults in a variable?

Am I missing something?

Answer 1

Possible reasons (for the second example)…

• Inherited ignorance… (saw it done that way, and copied the practice)

• Intrinsic ignorance… (saw it done properly as in your last code block, but replaced the cached object with an on-the-fly object and didn’t know that the empty object should be removed)

• Global warming.

• Lack of attention to detail… (similar to point 2, knows it isn’t necessary but never really took the time to examine the code)

• Global cooling.

• Overly defensive coding… (afraid that the defaults may someday be reworked into a reusable object, and is afraid that the empty object won’t be inserted at that time)

• jQuery developers always do what the voices tell them 😉

Overall, you’re right. The middle object is created, copied to an empty object, then discarded. It’s an unnecessary and wasteful practice.