Which to use when referencing in jQuery plugins - $(obj) vs obj

Question

I'm self learning and currently tackling jQuery plugins.

I've discovered a boiler plate that for iterating through elements on a page assigns $(this) to a global variable 'obj'.

var obj = $(this);

As a result in my functions I can use either $(obj).someFunc() or obj.someFunc() both work but if honest I don't really understand what the difference is.

So there's the question, what are the performance differences/benefits of both methods and which should I be using?

Answer 1

If obj is already a jQuery object, which is the case when you do var obj = $(this);, then there is no need to pass it to jQuery again.

$(obj) is the same as $($(this)), which is clearly redundant.

Having a look at jQuery's documentation ^[docs] also helps to understand what you can pass to jQuery (alias $):

• jQuery( selector [, context ] )
• jQuery( element )
• jQuery( elementArray )
• jQuery( object )
• jQuery( jQuery object )
• jQuery()

You see that passing a jQuery object is perfectly valid, but it will clone the passed object, which is probably not what you intend to do.

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However, it might be worth pointing out that inside a jQuery plugin method, this is already a jQuery object, so you don't have to pass it to jQuery either.

More info here: http://docs.jquery.com/Plugins/Authoring.