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John Chac..

jquery("#") or getElementById

in Using jQuery • 10 years ago

this may be discussed earlier...

I read jquery internally uses document.getElementById for $("#myDiv")

but below test case show huge performance difference between

$("#myDiv")
and
document.getElementById("myDiv")

http://jsperf.com/jqueryvsgetelemid/2

2.another scenario I tried is below where second part is faster.

$("#myDiv .blah"); vs $(document.getElementById("myDiv")).find(".blah");

http://jsperf.com/jquery-getbyid

So if somebody keen on performance, its better to use document.getElementById for selecting with id.

is it right?

Replies(2)

alano999

Re: jquery("#") or getElementById

10 years ago

Your findings are correct because jQuery lines up an assortment of library functions each time it creates a selection, and it is those library functions where the benefits of jQuery arises.

If you simply want to retrieve an element with a fixed name then vanilla JavaScript is going to be faster.

The key benefit of jQuery is that you can very easily cascade complex operations without ever needing to know something as inert and useless as the element's ID.

alano999

Re: jquery("#") or getElementById

10 years ago

On another note, it is dangerous to compare the two based purely upon speed of execution.

If you REALLY want speed, then you should be programming in Assembly Language. I spent most of the first part of my career programming assembly language for things ranging from personal computers to rail and bus ticket machines. It is fun and the code runs awesomely fast. However, doing anything takes a lot of effort and you soon learn to develop (or find) higher level libraries and languages to make life easier and development much faster.

Whilst typing this message, there are several "layers" of abstraction running to make the website easy to develop and maintain. At the top layer there is Zoho's discussion framework. Next layer down there is jQuery (actually, there may even be another level of abstraction between this and Zoho's Framework, perhaps something like Drupal?). Next layer down there is JavaScript. Next layer down is C++ (because Chrome's V8 JavaScript Engine is built upon that). Next layer down is Assembly Language.

Do not judge jQuery mainly by its speed. Like I said, if you really want speed, you should save your judgement and use Assembly Language. I can give yo a quick trainer course in X86 assembly language if you need it

Best wishes for your research.

Alan

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