When to use Vanilla JavaScript vs. jQuery?

Question

I have noticed while monitoring/attempting to answer common jQuery questions, that there are certain practices using javascript, instead of jQuery, that actually enable you

Answer 1

This is my personal view, but as jQuery is JavaScript anyway, I think theoretically it cannot perform better than vanilla JS ever.

But practically it may perform better than hand-written JS, as one's hand-written code may be not as efficient as jQuery.

Bottom-line - for smaller stuff I tend to use vanilla JS, for JS intensive projects I like to use jQuery and not reinvent the wheel - it's also more productive.

Answer 2

There's already an accepted answer but I believe no answer typed directly here can be comprehensive in its list of native javascript methods/attributes that has practically guaranteed cross-browser support. For that may I redirect you to quirksmode:

http://www.quirksmode.org/compatibility.html

It is perhaps the most comprehensive list of what works and what doesn't work on what browser anywhere. Pay particular attention to the DOM section. It is a lot to read but the point is not to read it all but to use it as a reference.

When I started seriously writing web apps I printed out all the DOM tables and hung them on the wall so that I know at a glance what is safe to use and what requires hacks. These days I just google something like quirksmode parentNode compatibility when I have doubts.

Like anything else, judgement is mostly a matter of experience. I wouldn't really recommend you to read the entire site and memorize all the issues to figure out when to use jQuery and when to use plain JS. Just be aware of the list. It's easy enough to search. With time you will develop an instinct of when plain JS is preferable.

---

PS: PPK (the author of the site) also has a very nice book that I do recommend reading

Answer 3

If you are mostly concerned about performance, your main example hits the nail on the head. Invoking jQuery unnecessarily or redundantly is, IMHO, the second main cause of slow performance (the first being poor DOM traversal).

It's not really an example of what you're looking for, but I see this so often that it bears mentioning: One of the best ways to speed up performance of your jQuery scripts is to cache jQuery objects, and/or use chaining:

// poor
$(this).animate({'opacity':'0'}, function() { $(this).remove(); });

// excellent
var element = $(this);
element.animate({'opacity':'0'}, function() { element.remove(); });

// poor
$('.something').load('url');
$('.something').show();

// excellent
var something = $('#container').children('p.something');
something.load('url').show();

Answer 4

The correct answer is that you'll always take a performance penalty when using jQuery instead of 'plain old' native JavaScript. That's because jQuery is a JavaScript Library. It is not some fancy new version of JavaScript.

The reason that jQuery is powerful is that it makes some things which are overly tedious in a cross-browser situation (AJAX is one of the best examples) and smooths over the inconsistencies between the myriad of available browsers and provides a consistent API. It also easily facilitates concepts like chaining, implied iteration, etc, to simplify working on groups of elements together.

Learning jQuery is no substitute for learning JavaScript. You should have a firm basis in the latter so that you fully appreciate what knowing the former is making easier for you.

-- Edited to encompass comments --

As the comments are quick to point out (and I agree with 100%) the statements above refer to benchmarking code. A 'native' JavaScript solution (assuming it is well written) will outperform a jQuery solution that accomplishes the same thing in nearly every case (I'd love to see an example otherwise). jQuery does speed up development time, which is a significant benefit which I do not mean to downplay. It facilitates easy to read, easy to follow code, which is more than some developers are capable of creating on their own.

In my opinion then, the answer depends on what you're attempting to achieve. If, as I presumed based on your reference to performance benefits, you're after the best possible speed out of your application, then using jQuery introduces overhead every time you call $(). If you're going for readability, consistency, cross browser compatibility, etc, then there are certainly reasons to favor jQuery over 'native' JavaScript.

Answer 5

$(this) is different to this :

By using $(this) you are ensuring the jQuery prototype is being passed onto the object.

Answer 6

Others' answers have focused on the broad question of "jQuery vs. plain JS." Judging from your OP, I think you were simply wondering when it's better to use vanilla JS if you've already chosen to use jQuery. Your example is a perfect example of when you should use vanilla JS:

$(this).attr('id');

Is both slower and (in my opinion) less readable than:

this.id.

It's slower because you have to spin up a new JS object just to retrieve the attribute the jQuery way. Now, if you're going to be using $(this) to perform other operations, then by all means, store that jQuery object in a variable and operate with that. However, I've run into many situations where I just need an attribute from the element (like id or src).

Are there any other common practices like this? Where certain Javascript operations could be accomplished easier, without bringing jQuery into the mix. Or is this a rare case? (of a jQuery "shortcut" actually requiring more code)

I think the most common case is the one you describe in your post; people wrapping $(this) in a jQuery object unnecessarily. I see this most often with id and value (instead using $(this).val()).

Edit: Here's an article that explains why using jQuery in the attr() case is slower. Confession: stole it from the tag wiki, but I think it's worth mentioning for the question.

Edit again: Given the readability/performance implications of just accessing attributes directly, I'd say a good rule of thumb is probably to try to to use this.<attributename> when possible. There are probably some instances where this won't work because of browser inconsistencies, but it's probably better to try this first and fall back on jQuery if it doesn't work.