I heard several times that jQuery's strongest asset is the way it queries and manipulates elements in the DOM: you can use CSS queries to create complex queries that would be very hard to do in regular javascript .
However , as far as I know, you can achieve the same result with document.querySelector or document.querySelectorAll, which are supported in Internet Explorer 8 and above.
So the question is this: why 'risk' jQuery's overhead if its strongest asset can be achieved with pure JavaScript?
I know jQuery has more than just CSS selectors, for example cross browser AJAX, nice event attaching etc. But its querying part is a very big part of the strength of jQuery!
Any thoughts?
document.querySelectorAll() has several inconsistencies across browsers and is not supported in older browsersThis 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 considered
var 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 notation
element.style.backgroundColor = "green" // or
element.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 155ms
Native 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!
That's because jQuery can do much more than querySelectorAll.
First of all, jQuery (and Sizzle, in particular), works for older browsers like IE7-8 that doesn't support CSS2.1-3 selectors.
Plus, Sizzle (which is the selector engine behind jQuery) offers you a lot of more advanced selector instruments, like the :selected pseudo-class, an advanced :not() selector, a more complex syntax like in $("> .children") and so on.
And it does it cross-browsers, flawlessly, offering all that jQuery can offer (plugins and APIs).
Yes, if you think you can rely on simple class and id selectors, jQuery is too much for you, and you'd be paying an exaggerated pay-off. But if you don't, and want to take advantage of all jQuery goodness, then use it.
jQuery's Sizzle selector engine can use querySelectorAll if it's available. It also smooths out inconsistencies between browsers to achieve uniform results. If you don't want to use all of jQuery, you could just use Sizzle separately. This is a pretty fundamental wheel to invent.
Here's some cherry-pickings from the source that show the kind of things jQuery(w/ Sizzle) sorts out for you:
Safari quirks mode:
if ( document.querySelectorAll ) {
(function(){
var oldSizzle = Sizzle,
div = document.createElement("div"),
id = "__sizzle__";
div.innerHTML = "<p class='TEST'></p>";
// Safari can't handle uppercase or unicode characters when
// in quirks mode.
if ( div.querySelectorAll && div.querySelectorAll(".TEST").length === 0 ) {
return;
}
If that guard fails it uses it's a version of Sizzle that isn't enhanced with querySelectorAll. Further down there are specific handles for inconsistencies in IE, Opera, and the Blackberry browser.
// Check parentNode to catch when Blackberry 4.6 returns
// nodes that are no longer in the document #6963
if ( elem && elem.parentNode ) {
// Handle the case where IE and Opera return items
// by name instead of ID
if ( elem.id === match[3] ) {
return makeArray( [ elem ], extra );
}
} else {
return makeArray( [], extra );
}
And if all else fails it will return the result of oldSizzle(query, context, extra, seed).
In terms of code maintainability, there are several reasons to stick with a widely used library.
One of the main ones is that they are well documented, and have communities such as ... say ... stackexchange, where help with the libraries can be found. With a custom coded library, you have the source code, and maybe a how-to document, unless the coder(s) spent more time documenting the code than writing it, which is vanishingly rare.
Writing your own library might work for you , but the intern sitting at the next desk may have an easier time getting up to speed with something like jQuery.
Call it network effect if you like. This isn't to say that the code will be superior in jQuery; just that the concise nature of the code makes it easier to grasp the overall structure for programmers of all skill levels, if only because there's more functional code visible at once in the file you are viewing. In this sense, 5 lines of code is better than 10.
To sum up, I see the main benefits of jQuery as being concise code, and ubiquity.
Here's a comparison if I want to apply the same attribute, e.g. hide all elements of class "my-class". This is one reason to use jQuery.
jQuery:
$('.my-class').hide();
JavaScript:
var cls = document.querySelectorAll('.my-class');
for (var i = 0; i < cls.length; i++) {
cls[i].style.display = 'none';
}
With jQuery already so popular, they should have made document.querySelector() behave just like $(). Instead, document.querySelector() only selects the first matching element which makes it only halfway useful.
Old question, but half a decade later, it’s worth revisiting. Here I am only discussing the selector aspect of jQuery.
document.querySelector[All] is supported by all current browsers, down to IE8, so compatibility is no longer an issue. I have also found no performance issues to speak of (it was supposed to be slower than document.getElementById, but my own testing suggests that it’s slightly faster).
Therefore when it comes to manipulating an element directly, it is to be preferred over jQuery.
For example:
var element=document.querySelector('h1');
element.innerHTML='Hello';
is vastly superior to:
var $element=$('h1');
$element.html('hello');
In order to do anything at all, jQuery has to run through a hundred lines of code (I once traced through code such as the above to see what jQuery was actually doing with it). This is clearly a waste of everyone’s time.
The other significant cost of jQuery is the fact that it wraps everything inside a new jQuery object. This overhead is particularly wasteful if you need to unwrap the object again or to use one of the object methods to deal with properties which are already exposed on the original element.
Where jQuery has an advantage, however, is in how it handles collections. If the requirement is to set properties of multiple elements, jQuery has a built-in each method which allows something like this:
var $elements=$('h2'); // multiple elements
$elements.html('hello');
To do so with Vanilla JavaScript would require something like this:
var elements=document.querySelectorAll('h2');
elements.forEach(function(e) {
e.innerHTML='Hello';
});
which some find daunting.
jQuery selectors are also slightly different, but modern browsers (excluding IE8) won’t get much benefit.
As a rule, I caution against using jQuery for new projects:
jQuery is an external library adding to the overhead of the project, and to your dependency on third parties.
jQuery function is very expensive, processing-wise.
jQuery imposes a methodology which needs to be learned and may compete with other aspects of your code.
jQuery is slow to expose new features in JavaScript.
If none of the above matters, then do what you will. However, jQuery is no longer as important to cross-platform development as it used to be, as modern JavaScript and CSS go a lot further than they used to.
This makes no mention of other features of jQuery. However, I think that they, too, need a closer look.
as the official site says:
"jQuery: The Write Less, Do More, JavaScript Library"
try to translate the following jQuery code without any library
$("p.neat").addClass("ohmy").show("slow");
I think the true answer is that jQuery was developed long before querySelector/querySelectorAll became available in all major browsers.
Initial release of jQuery was in 2006. In fact, even jQuery was not the first which implemented CSS selectors.
IE was the last browser to implement querySelector/querySelectorAll. Its 8th version was released in 2009.
So now, DOM elements selectors is not the strongest point of jQuery anymore. However, it still has a lot of goodies up its sleeve, like shortcuts to change element's css and html content, animations, events binding, ajax.
$("#id") vs document.querySelectorAll("#id")
The deal is with the $() function it makes an array and then breaks it up for you but with document.querySelectorAll() it makes an array and you have to break it up.
Just a comment on this, when using material design lite, jquery selector does not return the property for material design for some reason.
For:
<div class="logonfield mdl-textfield mdl-js-textfield mdl-textfield--floating-label">
<input class="mdl-textfield__input" type="text" id="myinputfield" required>
<label class="mdl-textfield__label" for="myinputfield">Enter something..</label>
</div>
This works:
document.querySelector('#myinputfield').parentNode.MaterialTextfield.change();
This does not:
$('#myinputfield').parentNode.MaterialTextfield.change();
Related
when it comes to modifying formatting and layouts (style sheets) why would jquery be more advantageous compared to plain javascript??
plain javascript already provides functions like "getelementsbyclassname" or "getelementsbyid" to get a handle for element objects, then why use the jquery interface?
i've read it's "easier"... exactly how?
"more efficient"? but it adds another layer of abstraction...
sure the library is quite easy to download the library since it's CDN-ed, but i want something that's even more minimalistic.
EDIT (after hearing ohcibi's response):
ANOTHER QUESTION: if i'm only concerned about modifying style sheets, would sizzle.js be a more minimalistic option? is it's implementation (as far as it's scope go) as complete as jQuery? does it execute faster?
To put it simply: Cross-browser compatibility, ease of writing/reading, more efficient coding, ubiquitous use.
Also, it doesn't replace ALL javascript. You can use javascript with it if you like or for some simple things that are recognized (more or less) universally by browsers.
Just to restate: more efficient coding.
It's not more minimalistic to write everything in plain js for all the different browser quirks that jquery does for you already. But feel free to do so if you have the time.
getElementsByClassname and so on do not provide full CSS3 featured selectors. Plus they are not 100% browser compatible.
If youre only interested into these selectors. Try sizzle.js, its what jQuery uses for the selection of elements.
In modern browsers, jQuery makes use of document.querySelectorAll() to boost performance when valid CSS selectors are used. It falls back to Sizzle if a browser doesn't support the selector or the document.querySelectorAll() method.
However, I'd like to always use Sizzle instead of the native implementation when debugging a custom selector. Namely, I'm trying to come up with an implementation of :nth-last-child(), one of the CSS3 selectors that are not supported by jQuery. Since this selector is natively supported by modern browsers, it works as described in the linked question. It is precisely this behavior that's interfering with debugging my custom selector, though, so I'd like to avoid it.
A cheap hack I can use is to drop in a non-standard jQuery selector extension, thereby "invalidating" the selector so to speak. For example, assuming every li:nth-last-child(2) is visible, I can simply drop that in, turning this:
$('li:nth-last-child(2)').css('color', 'red');
Into this:
$('li:nth-last-child(2):visible').css('color', 'red');
This causes it to always be evaluated by Sizzle. Except, this requires that I make an assumption of my page elements which may or may not be true. And I really don't like that. Not to mention, I dislike using non-standard selectors in general unless absolutely necessary.
Is there a way to skip the native document.querySelectorAll() method in browsers that support it and force jQuery to use Sizzle to evaluate a selector instead, that preferably doesn't employ the use of non-standard selectors? Likely, this entails calling another method instead of $(), but it's much better than a selector hack IMO.
You could just set it to null before jQuery loads so it thinks it's not supported:
document.querySelectorAll = null;
//load jquery, will trigger not supported branch
//Optionally restore QSA here (save a reference) if needed
This is supposed to make this evaluate to false
Demo: http://jsbin.com/asipil/2/edit
Comment out the null line and rerun, and you will see it will turn red.
Since you're developing the code for the selector yourself, could you not simply give it a custom name for the duration of the development cycle? Maybe give it your own vendor prefix or something? -bolt-nth-last-child()
That way, you'll know the browser definitely won't support it, so it should always fall into using Sizzle.
When you're done with the development cycle, you can drop the -bolt- prefix.
I know that's more of a work-around than an answer to the question, but it seems like the simplest solution to me.
It looks to be that jQuery.find defaults to sizzle. This will save you from destroying your environment by setting a native function to null.
https://github.com/jquery/jquery/blob/master/src/sizzle-jquery.js#L3
So you should be able to do the following and it will always go through sizzle.
$.find('li:nth-last-child(2)')
Which is faster and why? Selecting div (for plugin needs) by $('div[data-something]') or $('div.something')? I lean towards the former since it's "cleaner".
Based on this SO question I know I shouldn't be using both. However I didn't find out whether there is a difference between these.
In Chrome 16 at least, there is no difference. However, if you make the class selector less specific ($(".test") for example), it does outperform the other methods:
That was somewhat unexpected, because as ShankarSangoli mentions, I thought the div.test class selector would be faster.
It will vary by browser. Nearly all browsers now support querySelectorAll, and jQuery will use it when it can. querySelectorAll can be used with attribute presence selectors, so if it's there jQuery doesn't have to do the work, it can offload it to the engine.
For older browsers without querySelectorAll, jQuery will obviously have to do more work, but even IE8 has it.
As with most of these things, your best bet is:
Don't worry about it until/unless you see a problem, and
If you see a problem, profile it on the browsers you intend to support and then make an informed decision.
Selecting by class is always faster than attribute selector because jQuery tries to use the native getElementByCalssName first if supported by browsers. If not it uses the querySelector which uses css selectors to find the elements within the page.
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 to write less and do ... well the same amount. And may also yield performance benefits.
A specific example
$(this) vs this
Inside a click event referencing the clicked objects id
jQuery
$(this).attr("id");
Javascript
this.id;
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)
EDIT : While I appreciate the answers regarding jQuery vs. plain javascript performance, I am actually looking for much more quantitative answers. While using jQuery, instances where one would actually be better off (readability/compactness) to use plain javascript instead of using $(). In addition to the example I gave in my original question.
this.id (as you know)
this.value (on most input types. only issues I know are IE when a <select> doesn't have value properties set on its <option> elements, or radio inputs in Safari.)
this.className to get or set an entire "class" property
this.selectedIndex against a <select> to get the selected index
this.options against a <select> to get a list of <option> elements
this.text against an <option> to get its text content
this.rows against a <table> to get a collection of <tr> elements
this.cells against a <tr> to get its cells (td & th)
this.parentNode to get a direct parent
this.checked to get the checked state of a checkbox Thanks #Tim Down
this.selected to get the selected state of an option Thanks #Tim Down
this.disabled to get the disabled state of an input Thanks #Tim Down
this.readOnly to get the readOnly state of an input Thanks #Tim Down
this.href against an <a> element to get its href
this.hostname against an <a> element to get the domain of its href
this.pathname against an <a> element to get the path of its href
this.search against an <a> element to get the querystring of its href
this.src against an element where it is valid to have a src
...I think you get the idea.
There will be times when performance is crucial. Like if you're performing something in a loop many times over, you may want to ditch jQuery.
In general you can replace:
$(el).attr('someName');
with:
Above was poorly worded. getAttribute is not a replacement, but it does retrieve the value of an attribute sent from the server, and its corresponding setAttribute will set it. Necessary in some cases.
The sentences below sort of covered it. See this answer for a better treatment.
el.getAttribute('someName');
...in order to access an attribute directly. Note that attributes are not the same as properties (though they mirror each other sometimes). Of course there's setAttribute too.
Say you had a situation where received a page where you need to unwrap all tags of a certain type. It is short and easy with jQuery:
$('span').unwrap(); // unwrap all span elements
But if there are many, you may want to do a little native DOM API:
var spans = document.getElementsByTagName('span');
while( spans[0] ) {
var parent = spans[0].parentNode;
while( spans[0].firstChild ) {
parent.insertBefore( spans[0].firstChild, spans[0]);
}
parent.removeChild( spans[0] );
}
This code is pretty short, it performs better than the jQuery version, and can easily be made into a reusable function in your personal library.
It may seem like I have an infinite loop with the outer while because of while(spans[0]), but because we're dealing with a "live list" it gets updated when we do the parent.removeChild(span[0]);. This is a pretty nifty feature that we miss out on when working with an Array (or Array-like object) instead.
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.
There's a framework called... oh guess what? Vanilla JS. Hope you get the joke... :D It sacrifices code legibility for performance... Comparing it to jQuery bellow you can see that retrieving a DOM element by ID is almost 35X faster. :)
So if you want performance you'd better try Vanilla JS and draw your own conclusions. Maybe you won't experience JavaScript hanging the browser's GUI/locking up the UI thread during intensive code like inside a for loop.
Vanilla JS is a fast, lightweight, cross-platform framework for
building incredible, powerful JavaScript applications.
On their homepage there's some perf comparisons:
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
When:
you know that there is unflinching cross-browser support for what you are doing, and
it is not significantly more code to type, and
it is not significantly less readable, and
you are reasonably confident that jQuery will not choose different implementations based on the browser to achieve better performance, then:
use JavaScript. Otherwise use jQuery (if you can).
Edit: This answer applies both when choosing to use jQuery overall versus leaving it out, as well as choosing whether to to use vanilla JS inside jQuery. Choosing between attr('id') and .id leans in favor of JS, while choosing between removeClass('foo') versus .className = .className.replace( new Regexp("(?:^|\\s+)"+foo+"(?:\\s+|$)",'g'), '' ) leans in favor of jQuery.
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.
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();
I've found there is certainly overlap between JS and JQ. The code you've shown is a good example of that. Frankly, the best reason to use JQ over JS is simply browser compatibility. I always lean toward JQ, even if I can accomplish something in JS.
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.
The first answer's live properties list of this as a DOM element is quite complete.
You may find also interesting to know some others.
When this is the document :
this.forms to get an HTMLCollection of the current document forms,
this.anchors to get an HTMLCollection of all the HTMLAnchorElements with name being set,
this.links to get an HTMLCollection of all the HTMLAnchorElements with href being set,
this.images to get an HTMLCollection of all the HTMLImageElements
and the same with the deprecated applets as this.applets
When you work with document.forms, document.forms[formNameOrId] gets the so named or identified form.
When this is a form :
this[inputNameOrId] to get the so named or identified field
When this is form field:
this.type to get the field type
When learning jQuery selectors, we often skip learning already existing HTML elements properties, which are so fast to access.
As usual I'm coming late to this party.
It wasn't the extra functionality that made me decide to use jQuery, as attractive as that was. After all nothing stops you from writing your own functions.
It was the fact that there were so many tricks to learn when modifying the DOM to avoid memory leaks (I'm talking about you IE). To have one central resource that managed all those sort of issues for me, written by people who were a whole lot better JS coders than I ever will be, that was being continually reviewed, revised and tested was god send.
I guess this sort of falls under the cross browser support/abstraction argument.
And of course jQuery does not preclude the use of straight JS when you needed it. I always felt the two seemed to work seamlessly together.
Of course if your browser is not supported by jQuery or you are supporting a low end environment (older phone?) then a large .js file might be a problem. Remember when jQuery used to be tiny?
But normally the performance difference is not an issue of concern. It only has to be fast enough. With Gigahertz of CPU cycles going to waste every second, I'm more concerned with the performance of my coders, the only development resources that doesn't double in power every 18 months.
That said I'm currently looking into accessibility issues and apparently .innerHTML is a bit of a no no with that. jQuery of course depends on .innerHTML, so now I'm looking for a framework that will depend on the somewhat tedious methods that are allowed. And I can imagine such a framework will run slower than jQuery, but as long as it performs well enough, I'll be happy.
Here's a non-technical answer - many jobs may not allow certain libraries, such as jQuery.
In fact, In fact, Google doesn't allow jQuery in any of their code (nor React, because it's owned by Facebook), which you might not have known until the interviewer says "Sorry, but you cant use jQuery, it's not on the approved list at XYZ Corporation". Vanilla JavaScript works absolutely everywhere, every time, and will never give you this problem. If you rely on a library yes you get speed and ease, but you lose universality.
Also, speaking of interviewing, the other downside is that if you say you need to use a library to solve a JavaScript problem during a code quiz, it comes across like you don't actually understand the problem, which looks kinda bad. Whereas if you solve it in raw vanilla JavaScript it demonstrates that you actually understand and can solve every part of whatever problem they throw in front of you.
$(this) is different to this :
By using $(this) you are ensuring the jQuery prototype is being passed onto the object.
Back in 2005, Quirksmode.com released this article:
http://www.quirksmode.org/dom/classchange.html
that showed "proof" that changing the style of an element by changing its class (ie. "elem.className = x") was almost twice as fast as changing its style via its style property (ie. "elem.style.someStyle = x"), except in Opera. As a result of that article, we started using a className-based solution to do things like showing/hiding elements on our site.
The problem is, one of our developers would much rather use jQuery's equivalent methods for this kind of thing (ie. "$(something).hide()"), and I'm having a hard time convincing him that our className-based function is worth using, as I can only find a single article written four years ago.
Does anyone know of any more recent or more comprehensive investigations in to this issue?
Micro-optimization is evil. I think unless you are hiding a seriously large amount of elements at once or something, the difference in milliseconds is unimportant if by some chance that article is still relevant nowadays.
With that in mind, I would go with jQuery's methods as they are battle tested and more concise.
There is a flaw in the benchmark that article uses.
In my personal experience I've never seen a case where updating a className outperforms inline style setting. I have no concrete proof of this (I do vaguely remember an article I'm going to try to dig up), but I have noticed that large clientside apps (for example gmail, or google maps) prefer setting inline styles to classNames, and it was in the context of analysis of these apps that I first heard of the speed increase in doing so.
Note that I am not promoting one over the other: setting the className dynamically goes a long way in terms of maintainability/readability and separating concerns.
While I generally agree with the practice of using classes over style attributes for many reasons. Performance is one but consistency is another. I've often seen people do things like:
function toggle(element) {
element.style.display = element.style.display == 'none' ? 'block' : 'none';
}
(or the jQuery equivalent)
Seems reasonable right? It is until you apply it to table elements that have default display values of, for example, table-cell (not block). The class method:
.hidden { display: none; }
...
function toggle(element) {
$(element).toggleClass("hidden");
}
is much, much better for this and other reasons.
But the jQuery methods like hide() are an exception to this. They handle display setting correctly and give you the animations.
Test it yourself. There's a tester on the page you linked. Test performance on your target browsers to determine the best method to use, performance-wise.
Personally, I would choose readability over performance. Besides, the tides may turn later (if they haven't already**). If it makes sense to use a class (i.e. you use the style for many elements), you might as well use a class. If the CSS is for an animation on an element, use style. For either, prefer jQuery's functions as they are (1) more consistent and (2) more robust and tested.
**For Opera 10, at least, the speed has definitely improved. The tests are 5/12ms locally for Opera 10, 57/88ms for Firefox 3, 14/36ms for Google Chrome, and 125/118ms (!) for IE7. IE7 (perhaps your target browser) has about the same speed for either, with style changing slightly in the lead!
Premature optimization is the root of all evil.
Are you hiding hundreds of elements per second? If not, I'd say there are bigger fish to fry. Worse, a study done in 2005 says nothing about the performance of modern browsers. No IE7 or 8, No Firefox 3 (was 2 even out?), no Chrome.
But if you insist and want your fellow colleagues to follow suit, you should write a jQuery plugin that "hide()"'s using a class instead of a style.
No, but I can tell you that jQuery.hide() can hide an element with a smooth effect. This cannot be done by changing the className.
You are talking about client code, it runs in the user browser so it does not load your server. I ignore the javascript in your client side but I guess is not crunching much CPU.
Your coleague use of jQuery is probably not having a great impact while it results in a more readable code. Therefore I think he does not need to be convinced at all.