jQuery vs document.querySelectorAll

document.querySelectorAll() has several inconsistencies across browsers and is not supported in older browsers^{This probably won't cause any trouble anymore nowadays}. It has a very unintuitive scoping mechanism and some other not so nice features. Also with javascript you have a harder time working with the result sets of these queries, which in many cases you might want to do. jQuery provides functions to work on them like: filter(), find(), children(), parent(), map(), not() and several more. Not to mention the jQuery ability to work with pseudo-class selectors.

However, I would not consider these things as jQuery's strongest features but other things like "working" on the dom (events, styling, animation & manipulation) in a crossbrowser compatible way or the ajax interface.

If you only want the selector engine from jQuery you can use the one jQuery itself is using: Sizzle That way you have the power of jQuerys Selector engine without the nasty overhead.

EDIT:Just for the record, I'm a huge vanilla JavaScript fan. Nonetheless it's a fact that you sometimes need 10 lines of JavaScript where you would write 1 line jQuery.

Of course you have to be disciplined to not write jQuery like this:

$('ul.first').find('.foo').css('background-color', 'red').end().find('.bar').css('background-color', 'green').end();

This is extremely hard to read, while the latter is pretty clear:

$('ul.first')   .find('.foo')      .css('background-color', 'red').end()   .find('.bar')      .css('background-color', 'green').end();

The equivalent JavaScript would be far more complex illustrated by the pseudocode above:

1) Find the element, consider taking all element or only the first.

// $('ul.first')// taking querySelectorAll has to be consideredvar e = document.querySelector("ul.first");

2) Iterate over the array of child nodes via some (possibly nested or recursive) loops and check the class (classlist not available in all browsers!)

//.find('.foo')for (var i = 0;i<e.length;i++){     // older browser don't have element.classList -> even more complex     e[i].children.classList.contains('foo');     // do some more magic stuff here}

3) apply the css style

// .css('background-color', 'green')// note different notationelement.style.backgroundColor = "green" // orelement.style["background-color"] = "green"

This code would be at least two times as much lines of code you write with jQuery. Also you would have to consider cross-browser issues which will compromise the severe speed advantage (besides from the reliability) of the native code.

If you are optimizing your page for IE8 or newer, you should really consider whether you need jquery or not. Modern browsers have many assets natively which jquery provides.

If you care for performance, you can have incredible performance benefits (2-10 faster) using native javascript:http://jsperf.com/jquery-vs-native-selector-and-element-style/2

I transformed a div-tagcloud from jquery to native javascript (IE8+ compatible), the results are impressive. 4 times faster with just a little overhead.

                    Number of lines       Execution Time                       Jquery version :        340                    155msNative version :        370                    27ms

You Might Not Need Jquery provides a really nice overview, which native methods replace for which browser version.

http://youmightnotneedjquery.com/

Appendix: Further speed comparisons how native methods compete to jquery

• Array: $.inArray vs Array.indexOf: Jquery 24% slower

• DOM: $.empty vs Node.innerHtml: Jquery 97% slower

• DOM: $.on vs Node.addEventListener: Jquery 90% slower

• DOM: $.find vs Node.queryselectorall: Jquery 90% slower

• Array: $.grep vs Array.filter: Native 70% slower

• DOM: $.show/hide vs display none: Jquery 85% slower

• AJAX: $.ajax vs XMLHttpRequest: Jquery 89% slower

• Height: $.outerHeight vs offsetHeight: Jquery 87% slower

• Attr: $.attr vs setAttribute: Jquery 86% slower

To understand why jQuery is so popular, it's important to understand where we're coming from!

About a decade ago, top browsers were IE6, Netscape 8 and Firefox 1.5. Back in those days, there were little cross-browser ways to select an element from the DOM besides Document.getElementById().

So, when jQuery was released back in 2006, it was pretty revolutionary. Back then, jQuery set the standard for how to easily select / change HTML elements and trigger events, because its flexibility and browser support were unprecedented.

Now, more than a decade later, a lot of features that made jQuery so popular have become included in the javaScript standard:

• Instead of jQuery's $(), you can now now use Document.querySelectorAll()
• Instead of jQuery's $el.on(), you can now use EventTarget.addEventListener()
• Instead of jQuery's $el.toggleClass(), you can now use Element.classList.toggle()
• ...

These weren't generally available back in 2005. The fact that they are today obviously begs the question of why we should use jQuery at all. And indeed, people are increasingly wondering whether we should use jQuery at all.

So, if you think you understand JavaScript well enough to do without jQuery, please do! Don't feel forced to use jQuery, just because so many others are doing it!