is jquery .find always useful?

Question

I have some HTML like this:

<div id="MyDiv">

  <div class="Class1">
    <div class="SClass1"></div>
  </div>
  <div class="Class2"></div>

</div>

Is there any difference between

$('#MyDiv').find('.SClass1').show();

and

$('#MyDiv .SClass1').show();

Answer 1

http://api.jquery.com/jquery/#selector-context states that:

Internally, selector context is implemented with the .find() method, so $('span', this) is equivalent to $(this).find('span').

Which means

$('#MyDiv .SClass1').show();

Is only one step away from jQuery internally making it

$('#MyDiv').find('.SClass1').show();

View this jsPerf test case to see the differences in speed

---

As @Dominic mentioned in the comments, in his jQuery Anti-Patterns for Performance & Compression presentation, Paul Irish states:

Selector Optimization

Of course, descending from an #id is best

// #id-based selector 
var arms = $('#container div.robotarm');

// hyper-optimized #id case first, then find: 
var arms = $('#container').find('div.robotarm');