选择涉及父级的jQuery元素

Question

Consider following scenarios and jQuery usage variants:

HTML

<ul class="wrapper">
    <li class="item">item 1</li>
    <li class="item">item 2</li>
    <li class="item">item 3</li>
    <li class="item">item 4</li>
</ul>

Usage a.

$('.wrapper').find('.item').addClass('active');

Usage b.

$('.item', '.wrapper').addClass('active');

My questions are

• Are they identical, in terms of functionality?
• Is one perform better than the other?
• Assuming they are identical, which one is considered as a better practise?

Answer 1

This $('.item', '.wrapper').addClass('active');

would be internally translated as

$('.wrapper').find('.item').addClass('active'); .

So i am sure that there is no difference between them.

//HANDLE: $(expr, context) 
//(which is just equivalent to: $(context).find(expr)

I just found the above comments in the jquery source

Answer 2

Performance result may be useful http://jsperf.com/