$('#id tag') vs. $('#id').find('tag') - which is preferable?

Question

I want to know which option is better, particularly in terms of their speed:

$(\'#id tag\')...

or

$(\'#id\').find(\'tag\')         


        

Answer 1

Here's the test case HTML where I look for all span elements under #i element:

  testL1_1
  testL1_2
  

    testL2_1
  
  

    

      testL3_1
    
  
  

    

      

        

          testL5_1
        
      
    
  

Testing these three jQuery selectors:

$("#i span");         // much slower
$("#i").find("span"); // FASTEST
$("span", "#i");      // second fastest

http://jsperf.com/jquery-sub-element-selection

I've run it on Google Chrome and Firefox and it seems that .find() is the fastest closely followed by the third case and much slower first one.