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Is it necessary to learn JavaScript before learning jQuery? [duplicate]

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Is it a good idea to learn JavaScript before learning jQuery?
I am about to start learning JavaScript. However one friend suggested me to go in for jQuery instead since he says future is jQuery. I heard that jQuery is created from JavaScript.
In short, give me one simple reason why developers like me should invest in JavaScript. What is its future?

Part of being a good programmer is having an interest in understanding how things work. You can't understand how JQuery works without knowing JavaScript.
A good programmer has a diversity of skills. Knowing both the JQuery way to do things and the JavaScript-only way makes you more versatile.
Most employers who are looking for someone who knows JQuery are probably also looking for someone who knows ordinary JavaScript.
You can never achieve true expertise in JQuery without understanding JavaScript.
Sometimes even a fairly lightweight framework is more than you need.
If you don't ever learn to do things the hard way, you won't appreciate what's so great about doing it the easy way.
Moreover, if you start by learning to do things the easier way, you'll have that much harder a time motivating yourself to learn to do it the hard way.
Learning the language first without the fancy frameworks builds character.
Who knows, maybe you'll want to make your own framework someday. Or even work on a new version of JQuery. To do that, you'll need to know the language.

jQuery is JavaScript and yes, it makes things a lot easier for you and you can use it without much JavaScript knowledge, and yes, it will probably become even more popular in the future.
BUT: Wherever is jQuery, there will be JavaScript. jQuery is "just" a tool. You still need "plain" JavaScript to solve some problems, e.g. string manipulation.
Imho: You cannot master jQuery if you don't master JavaScript.
And there will be situations where jQuery might be not the best solution, e.g. when you really need high performance.
For me, this is similar to other questions I read here on SO about web frameworks and programming languages, like: Do I have to learn/know PHP if I want to use [Zend | symfony | CodeIgniter].
Seriously: If you don't understand the basics, you cannot use a tool efficiently.

JQuery is a library, written in Javascript, the language. It is almost always the case that learning the library without learning the language is impractical if not impossible, irrespective of the library and the language in question.

jQuery will come and go.
You are a web developer, right? Javascript is huge. Think how much time people spend using a web browser. The entire time they are interfacing directly with html dom, css, and javascript. Or, less and less, flash and "actionscript" (which is basically javascript).
Learn javascript, learn css, learn the dom. Refer to ecma-262 versions 3 and 5 and publications by w3c and whatwg. Read mozdev, cross-check msdn.
After that, take a look at jQuery if you want. You will probably find that you don't need it for 99% of the stuff people use it for.

Every browser has its own implementation of Javascript ( the language ) and the DOM ( library for manipulating elements on the page ). Because of the inconsistency of each browsers Javascript + DOM with another, jQuery ( created with Javascript ) was created as a wrapper that internally deals with these inconsistencies so you can use the easy API.
Underneath the hood, most of your problems are already solved for you so you don't have to think about issues like:
invoking functionality for the DOM ready event
a consistent way of attaching event handlers for click, mouseover and other events, attaching multiple functions to the same action
returning the proper values for elements as well as viewport ( window ).
Because jQuery is a Javascript library you won't master it without mastering Javascript. See my previous answer for recommendations for learning Javascript.

You do not need to know JavaScript in order to use jQuery.
This depends what you want of course.
If you want to put together web pages and don't consider yourself the 'programming type' or you simply don't like JavaScript, then don't bother, spend your time where it will matter most.
Your also asking this question on a site where majority of users are developers so your going to get a lot of people who say you should learn JavaScript, I say learn it if it interests you.
There are pleanty of jQuery solutions out there and support so that you don't need JavaScript.

jQuery IS JavaScript. When you are writing jQuery, you are writing in javaScript. All a library like jQuery consists of is a premade collection of functions you can use in your JavaScript programs.
So, you have to know JavaScript syntax and the core language in order to use jQuery at all. A good book for that is Douglas Crockfords the Good Parts.
What you do not need to know as much about is the DOM API, since that is mainly what jQuery smooths over for you. It helps a lot to understand the concepts of the DOM, though. You still need to know what an element is, and what attributes are.
You also need to know about CSS in order to use jQuery effectively. The key concepts here are classes, IDs, positioning, visiblity and display, among others.

Yes you CAN use jQuery without knowing JavaScript. In fact, I knew very little about JavaScript originally but by using jQuery it sparked my interest to learn it and so I did. Years later I can say I am very proficient with both.

As you progress in your programmer expertise you would find that you go from library writer to library user. This is quite natural and OK. When you are starting off, all you have is the basics. You write your code in terms of those basics and over time find that you need to bunch common code in a library for easier reuse.
Sometime later you find that someone has already done just that and created a library that's even better than yours. You then switch from being library writer to library user. jQuery is one such library and you really need to know JavaScript to be able to draw a line in your head as to where jQuery is and where JavaScript is.
My advice, in light of the above, would be to learn the underlying technology before getting started with the library (which is what jQuery is). However in this case I would make an exception - skip DOM manipulation. DOM is a stupid abstraction and will have you tear your hair out in no time flat. jQuery wraps it up quite nicely, might as well get stuck into that after you understand JavaScript basics.

you can read this
edit
However one friend suggested me to go
in for jQuery instead since he says
future is jQuery.
If you go for jQuery, of course you are still learning Javascript...
You can not understand jQuery if you can not understand how Javascript works.
Some programmers learning jQuery wihtout the knowledge of javascript thought that they are learning a new programming scripting language. But they did not know that jQuery is not. They are just using jQuery as a tool. They are still coding Javascript...
If you want your Javascript codes to be cross-browser,
with less hassle, go for jQuery... but still you need the basic (or at least) knowledge of Javascript.

Is plain vanilla JavaScript better than using frameworks like jQuery or MooTools? [closed]

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Closed 11 years ago.
I am wondering if it is a good idea to rely on frameworks like jQuery or MooTools or should we just use plain JavaScript?
Apart from avoiding the re-invention of wheel, do they add any specific value?
Since the frameworks are open to the public, can there be possibility of exploitation of any security holes that might appear (of course, unintentionally :) ) in the frameworks?
Are there any other points that are to be considered when choosing a framework or otherwise?

Frameworks solve cross-browser bugs which normally would cost hours of your time, so you can focus on functionality instead of worrying about some edge case browser bug.. instead of wasting 4-5 hours solving a bug spend that time with your family.
Frameworks such as jQuery are pretty loaded with stuff like animation, selectors, html manipulation so there's usually some sort of functionality already built into the library, again saving you more time and the API makes it really easy to actually accomplish complex things.
Interpreters and browsers are only getting faster and faster so I don't particularly think it's a huge issue loading an entire library up. In addition thanks to Google et al we get very fast cdns and nowadays lots of sites are using the same exact URI to pull the script in, meaning there's a higher rate of the script getting cached and reused on another site.
Instead of every single web developer having their own library it's much more efficient having thousands of people concentrated to bettering a handful of libraries so cross-browser bugs get documented and fixed.
Competition is a good thing, the result of the slickspeed tests resulted in much faster selector engines such as Sizzle. Developers not having to worry about trivial DOM bugs means more complex libraries are created daily, which means entry-level developers have access to very powerful plugins.
As far as security, jQuery for example will detect if the browser is capable of parsing JSON natively and if so, rely on that. Usually any modern browser will have this, and it's much safer than eval... so jQuery strives to use the safer and more secure methods first. It will only use eval if there isnt a JSON.parse method available.
An important thing to remember in jQuery though is remembering you're still coding in Javascript. Usually people get too caught up in the sugar coated methods and wrapping everything in $, I think it's important to know you can still do this.href instead of $(this).attr('href') if you would like an absolutely normalized uri for example.

Do not downplay the importance of avoiding the re-invention of the wheel. You don't invent a new computer each time you want to write a new program.
But apart from that, JavaScript libraries provide better cross-browser support. This is extremely helpful, as a quick look at QuirksMode will demonstrate.
JavaScript frameworks make many things easier. Look at the jQuery documentation and you will see how easily it is do many fancy things.
JavaScript frameworks have been extended by many people, so there are many high quality jQuery plugins (for example — it's the framework I know the best) that you can use without having to write them yourself.
It is unlikely that JavaScript frameworks would introduce security holes, as they don't expose any more functionality than what you can do with plain JavaScript.

The frameworks provide a cross-browser-API for JavaScript, so most of the time they are very usefull even though they come with a little speed-loss. But the JS-Engines get fast almost every update so that's not really a problem.
There are also very many plugins for the frameworks so they not only provide an API but also new cross-browser-features.
But it depends on what you wanna do.

I don't give great weight to the "Open Source is extra-vulnerable to security issues" argument. I see benefit of many Good Guys reading the code and spotting such problems. If this were an issue then we'd need to discard Linux, Apache, MySql, and most of the Java libraries.
Frameworks generally save a very great deal of effort, I see them precisely as a pre-invented wheel. They don't need any other value.

It depends on what you're using JavaScript for. If you want to be able to show and hide panels, animate stuff, attach events to multiple elements, do Ajax, etc. then you need to consider cross-browser issues.
jQuery eliminates the need to think about cross-browser issues and allows some really neat functionality like the above and also modal dialogs, etc.
So it depends on what you want from JavaScript.

I have never used MooTools so can't comment on that, but jQuery makes a lot of things easier.
Selecting collections of objects by class, name, partial Id, etc.
Simplify Ajax calls.
Wireup event handlers to handle onclick, mouseover, mouseout, etc. and assign to elements based upon general selectors so that the logic can be reused.
Tons of transitions and other visual stuff to pretty up the front end.
There are a lot more, but it generally simplifies/accelerates development. One thing to watch out for is if you are using a ton of selectors in a single function (loop that iterates over the DOM 40+ times) it is waaay more efficient to use vanilla JavaScript.
So my advise would be to code the front end with the aid of a framework and then optimize the underperforming parts by subing in vanilla JavaScript.
Also, I don't see how jQuery or MooTools could be a security threat as they are client side frameworks, not server side. Remember to always validate inputs on the server side in addition to any client side validation and to properly parameterize SQL queries that are constructed on the server side.

How to become a good javascript coder [closed]

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I'm a self learner in javascript and I'm currently following the lessons in the book named "Beginning javascript 3rd edition" by Paul Wilton.
So far I've advanced myself towards chapter 4: Javascript - An object based language, and I did follow and solve the exercises provided inside the book. I tried to write a calculator myself, and by modifying and changing the code, every time I learn something new to enhance it.
How can I become good in javascript coding? Is there any special approach? Is there any concept or things I should learn first? What kind of study/career path should I follow for javascript? Anything I should be aware of?
I really have the courage to continue learning javascript, I just need some guidance.
I don't mind any expert opinion given, or pointing out any mistakes regarding this question, as I know that through my mistakes, I always learn something.

Consider JavaScript as a true
programming language
Learn the
difference between Object-Oriented
and Prototype-Oriented languages
Make sure you understand how
JavaScript (language) is related to
DOM (API) and never mix things up
Don't jump into "using jQuery to
solve all JavaScript problems" as
jQuery does not solve any problems
of JavaScript but rather those of
DOM

A very good way to learn (not restricted to JavaScript) is to have projects where you need to do something with the language (in your case JavaScript) you haven't done or haven't tried.
I have noticed that I improve a lot when I have a project and have to do something I am not really familiar with or I am not that great at. Last project required the use of web services with php, something I had rarely used, but this made be learn and study and just try to get better, which I did.
So my advice is try to have a project where you have to do something with JavaScript that you have no idea how to to.

JavaScript is unlike most other languages. While it is Object Oriented, it is weakly typed. This provides much greater flexibility, but at the same time, limits itself.
Keep a few sites in your pocket:
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide
http://javascript.crockford.com/
http://www.addedbytes.com/cheat-sheets/javascript-cheat-sheet/
One last thing:
Be aware of Douglas Crockford. Read his books. Read anything you can find with his name on it.

Conquer Level 1 First...The Princess can wait!
I would just do what is necessary first. Don't bother with the advanced stuff unless it's absolutely necessary. Most of the things you'll use JavaScript for are very top-level and superficial. Get the syntax, loops, types, etc all down first. Don't confuse yourself with the more difficult aspects of it until you've conquered level 1.
Then Move on to Common Solutions to Common Problems
I would even suggest learning something like jQuery before trying to learn how to extend prototypes, etc. Make yourself useful immediately by learning the stuff you'll be using frequently, and tackle the difficult stuff at a later date when you've got the time.

The same way you become a better programmer/writer:
Read a lot, write a little. Repeat ad nauseam.
Also, read this other related answer.

If you are starting on Javascript, I would recommend you going to this website.
However, if you already know bit of javascript, then it all depends on practice. This is the only way i know of that can make you a good programmer. And this apply to just about anything and any programming language.
Try to come up with your ideas and materialize them using Javascript.
How about building your own lightbox?
How about creating your own table filtering/sorting?
And how about all the cool stuff you might have in your mind?
Thanks :)

Program a lot
Read JavaScript: The Good Parts
Use JsLint!
Go to 1

I would suggest you try to go through following:
1. Book -Javascripts: the good Parts by douglas Crockford. Make sure you understand the points he raises in the book and try to implement them accordingly.
2. Do not just try to javascript functions for website validations; as static functions in javascript is the worst thing a developer can do.
3. Try to implements OOPs concepts in Javascript and see how using functions you can model your objects and their behavior.
4. I would highly recomment small design patterns problems to be solved in javascript, as that would bring out the understanding of functions and invocation patterns in javascript.
Hope it helps.
Focus is objects oriented nature of javascript and not just the syntax

It also helps also to install firebug and try out different things in the console.

Start with Javascript : Definitive
Guide . Pay special attention to the 1st
part core language features
Check crocford blog/site with the reading of this book
Now the time is for Javascript:Good parts
For More in depth knowledge check the ECMAScript3 and 5 refrence
Finally, try to learn some other prototype based language as well like self
For DOM API's check other parts of Javascript : Definitive
Guide and sites of respective browsers

I'm surpised with the comments here about learning Javascript. Let's not forget - you don't want to learn it all! While the language is quite great if used correctly, it has a tainted history and many horrid parts. Luckily, you really only have to listen to a single voice:
Douglas Crockford also wrote The Good Parts, which is a nice little Javascript book. He does a bunch of stuff at Yahoo! and has materials on their YUI Theater that explain the problem quite well:
http://developer.yahoo.com/yui/theater/

This is a really great read:
https://developer.mozilla.org/en/a_re-introduction_to_javascript

For beginners w3schools or tizag.com would be more better choice ..
Answer by Sergey is completely agreeable to me .. It is a good approach ..
All the best friend .. :-)

I think that Object-Oriented JavaScript by Stoyan Stefanov is an amazing book, but that could just be me.

I'd suggest you the definitive guide to the language of your choice!
Please ignore any kind of javascript style kind of programming that may be fashion today.
Just learn the language! Fashions may change, and if you know the language, then you know something that resists, rather then samething that is fashion for some predeterminate time....
For example, read this book! Take the time, and you will reach the next level ;-)

Like with everything else: learn and practice.
How to learn the others already wrote.

I would suggest finding a javascript framework and learning how to use it. Then you can see practical applications to how javascript works in real life. It will give you practical applications, and a much more specific (and larger) set of answers to "how to I..." type problems.
jQuery is a good framework to begin with, YUI and/or Prototype are good if you really want to dig in -- those two are meant for building your own resources, whereas jQuery is more focused on being easily usable.
Modern javascript is heavily about "prototyping" javascript to build in new functionality that's not included in its implemented specification. In other words, it moves beyond the basics of how to code in javascript found in most books and into the realm of "how to make javascript do more than it was intended to do." But the basics are a must if you intend on prototyping the language.
If you want to learn javascript purely for servicing clients and making better websites, then it really depends on how you learn. Personally, I learn more through practical application than just reading and exercises. If you're the same, then I suggest reading through (not working through) your book and meanwhile do a lot of reading up. I suggest "yui vs. prototype vs. jquery" as a starting Google search.
Think up a simple project you'd like to do, and then try and implement as many cool javascript features into that project as you can (ajax form submissions, automatically updating graphics based on form selections, image zoom, and animated fade effects some to mind as the most practically useful).
Again, it really depends on what your goals are -- do you want to become a contributor to a framework like jQuery, write plugins, or just know enough to implement functional javascript on a client website and look good on a resume. If it's the latter -- pick a framework, learn it. jQuery is the most user-friendly, Prototype is the most functional, YUI is as functional as Prototype, well supported, and a great up-and-comer.

You may want to look into major Javascript frameworks such as JQuery and MooTools. Understand the differences between them and pick your favorite.
Here are some links :
http://jqueryvsmootools.com/
http://blog.creonfx.com/javascript/mootools-vs-jquery-vs-prototype-vs-yui-vs-dojo-comparison-revised

Why is jQuery so widely adopted versus other Javascript frameworks? [closed]

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Closed 10 years ago.
I manage a group of programmers. I do value my employees opinion but lately we've been divided as to which framework to use on web projects.
I personally favor MooTools, but some of my team seems to want to migrate to jQuery because it is more widely adopted. That by itself is not enough for me to allow a migration.
I have used both jQuery and MooTools. This particular essay tends to reflect how I feel about both frameworks. jQuery is great for DOM Manipulation, but seem to be limited to helping you do that.
Feature wise, both jQuery and MooTools allow for easy DOM Selection and Manipulation:
// jQuery
$('#someContainer div[class~=dialog]')
.css('border', '2px solid red')
.addClass('critical');
// MooTools
$('#someContainer div[class~=dialog]')
.setStyle('border', '2px solid red')
.addClass('critical');
Both jQuery and MooTools allow for easy AJAX:
// jQuery
$('#someContainer div[class~=dialog]')
.load('/DialogContent.html');
// MooTools (Using shorthand notation, you can also use Request.HTML)
$('#someContainer div[class~=dialog]')
.load('/DialogContent.html');
Both jQuery and MooTools allow for easy DOM Animation:
// jQuery
$('#someContainer div[class~=dialog]')
.animate({opacity: 1}, 500);
// MooTools (Using shorthand notation, you can also use Fx.Tween).
$('#someContainer div[class~=dialog]')
.set('tween', {duration: 500})
.tween('opacity', 1);
jQuery offers the following extras:
Large community of supporters
Plugin Repository
Integration with Microsoft's ASP.NET and VisualStudio
Used by Microsoft, Google and others
MooTools offers the following extras:
Object Oriented Framework with Classic OOP emulation for JS
Extended native objects
Higher consistency between browsers for native functions support.
More easy code reuse
Used by The World Wide Web Consortium, Palm and others.
Given that, it seems that MooTools does everything jQuery does and more (some things I cannot do in jQuery and I can in MooTools) but jQuery has a smaller learning curve.
So the question is, why did you or your team choose jQuery over another JavaScript framework?
Note: While I know and admit jQuery is a great framework, there are other options around and I'm trying to take a decision as to why jQuery should be our choice versus what we use right now (MooTools)?

That's an odd question... I get the impression that...
you are very familiar with mootools and take full advantage of its OOP model, making your code easier to manage and support already.
you realise that jQuery's purpose is somewhat different and tweaked towards DOM manipulation and AJAX and that mootools does do everything jQuery does AND then some.
sounds as if you do not need to be using much in the way of 3-rd party plugins which makes the points of jQuery's popularity and support a bit less important.
Bottom line, is it the hype? jQuery is turning into one of these magical marketing buzzwords like 'AJAX', .NET and Web 2.0 — which is great for them but why do you need to justify staying with the framework that works so well for you? There's also the business considerations which I imagine will cover things like:
framework longevity, or is mootools likely to go away in the face of the ever growing jQuery — very doubtful, seeing as they just released 1.3 beta 1 and have 2.0 is in the pipelines for release by the end of the year.
cost of staff and their training (I imagine finding mootools programmers will be more difficult than these that slap jquery on their C.V / resume).
time (and cost) taken to maintain and extend your systems under each framework given your resources.
Both frameworks are great but I believe your interests are best served in staying with mootools.

Personally, jQuery does exactly what I need.
I try to do most of my stuff in my server-side code, which is well structured: it has proper OOP, layers, and an MVC architecture. When I need to do something with Javascript, I have found (so far) that jQuery has what I need. Frankly, that falls into three categories:
Simple DOM manipulation, usually showing/hiding stuff without hitting the server.
Ajax calls, nuff said.
UI perks, including modal popups, animations, fading transitions from/to hidden/shown. I am a hardcore backend coding guy, and I suck at UI stuff. I really like that jQuery lets me programmatically make stuff that looks appealing.
On top of that, the jQuery plugin library is huge, and I've found quite a few libraries that simplify my client-side work. Good stuff.
MooTools introduces OO thinking, which is nice, but not what I need. I want to keep my structuredness all on the backend, and not have to introduce that thinking to my client-side code. To me, client-side code is a very small piece of the emphasis and thinking about it from a Class-point-of-view is way overkill, and way more work. I feel like I'd be building two applications instead of one if I were to use what I'd think would be best practices for MooToools.
I think that sums up why its so popular, especially around here. By and large, we're backend code-y type people, and jQuery lets us make an appealing UI programmatically, and lets us focus on our backend core.

I'm not a fan of imposing classical object orientation onto JavaScript. There are so many ways to do it that one JavaScript Programmer might be using Base2 for OO, while another uses Prototype or Moo or JS.Class or Joose. Resig deliberately decided not to add classes to jQuery, and that has encouraged people to find more native JavaScript ways to solve problems.
As a result, it's easier for me to read JavaScript other jQuery writers write, and to write jQuery code that's easier for others to read. I typically don't try to emulate class OOP in JavaScript. Instead, I create objects on the fly and pass them around, and I have lots of arrays of objects. It's so easy to understand that I've even found myself carrying that thinking over to OOP languages!
For all I know Moo may very well have caught up with jQuery or surpassed it. But I can't spend my time tracking the 6 or 7 great JavaScript libraries to see which horse is ahead.
I think it's was largely a matter of timing. When masses of programmers jumped into AJAX, jQuery was the hot new cool thing that solved their problems.
Other libraries have largely caught up. YUI, ExtJS, Dojo, Moo--they're all great. But I can't use them all.
I work hard enough trying to figure out the ramifications of the new features of the library I do use. For instance, jQuery added Live events as of 1.3. This actually let me cut code from many pages. Does Moo offer that now too, and how am I supposed to know it happened, if it did?
I'm sure Moo is awesome. I'd love to have the time to learn it. But have you looked at Dojo? I had to use it on one project and found that it had pulled in most of the great ideas from jQuery as well. And it has pubsub and good support for Comet.
I sympathize with you. But your programmers are talking sense. Learning jQuery is good for their careers, and there are more books, examples, and fellow programmers to ask for help if they use jQuery.
If you decide to go jQuery after all, think hard before deciding whether to tack on an OO library. There are some cool ones (like JS.Class or Joose), but taking that step means isolating yourself from how most JavaScript programmers code.

I've been asking myself this very same question for a while now, by means of just trying to wrap my head around the argument. And with ever discussion I read, the overwhelming response has been "More widely adopted - therefore better".
I am one who uses both extensively. JQuery at work (adopted because it was "more widely adopted") and Mootools on personal projects. As a result, I constantly find myself feeling crippled when using JQuery; Be it with JSON support, element creation, event handling... and so on. At work, I find myself writing chains 75 events long... and I feel dirty as a result.
My main overall beef with JQuery though, is that there's a lack of consistency or practice where plug-ins and 3rd party developers are concerned. The anecdotal "More plug-ins are available" really doesn't help me when there's no consistency between the plug-ins, structurally or otherwise. It took me several weeks to learn the "accepted" plug-in model, and even then, I've adapted my own pragmatic style into it, as I find error and inefficiency within the current structures. It can be said that it's a 'Pro' that anyone can jump in and start JQuerying it up. However, I am more inclined to call that a 'Con', in that you will see 30 different ways to accomplish something, and it's difficult to pin an accepted standard.
So what does it mean to "Know JQuery", Does it mean you know how to rock a little .hide().show().fadeIn().fadeOut()?
When I have to get gangster on my JS at work, I miss me some Mootools. I mean no Native JSON support? C'mon......
In response to the "Widely adopted" response, we all know OSCommerce is the most "Widely Adopted" shopping cart, and we all know what a pile of shit that is. I'm in no way comparing JQuery to OSCommerce. I'm simply pointing out the faulty of "Widely Adopted" response.
As for plugins, the App store for apple has what... 100k apps? 50,000 are fart apps. Sure there's a lot of plugins to JQuery, but the ratio of trash to worth-while is great.

jQuery gives you access to crisp and concise functional programming methods. Since the release of method chaining in (LINQ) in C# 3.0 this works very well for .NET programmers. So the flow from one language to the next is easy. To be able to query the DOM for an object, or a list of objects, works much better for us. It is jQuery's selection power first that makes it so attractive, then the extendability of it, and of course all the built in features that come with it are nice. Also, the community behind is wonderful in that I first look to see if someone else did something and then attempt to do it myself if a solution was not found. And last...but certainly not least...the fact that Microsoft is going to include in in Visual Studio 10 and support it is great. Moo Tools, Prototype, etc. just can't compete with all of the above.

JS frameworks are so much alike, anyway. If you've been working with mootools for some time, stick to it. Knowing your framework is much more important than choosing one because of this or that.
In my opinion, mootools is better for advanced javascript programmers, while jquery is better for non-javascript programmers. That's what I think after reading both documentations, mind you, I didn't use any of them. jQuery lacks support for the core of javascript, function binding, object cloning, thread stacking, to name a few.

jQuery, like any framework, does what it does and if it doesn't fit your needs you should use something else. I don't use jQuery to do complicated programming in javascript, I use it because it makes DOM manipulation and CSS3 style stuff simple and 95% of the time that is what I need.

I have not looked at MooTools in a while either. But here are my points for JQuery:
Consistent programming model (there is a JQuery way that works)
Excellent documentation. When I started JQuery had the best documentation out there.
Extensive 3rd party plugings
Microsoft support -- I am an asp.net developer, this helps ease clients minds. Plus it ships with my tools now.
Lots of getting started guides.
JQuery's website looks nicer than MooTool's web site. I'm sorry that matters, but it does. Remember, many of these tools need to appeal to designers as well as developers.

YAGNI.
Yes, it's kinda out of place here, but that's the main reason jQuery has a larger base than MooTools. All those extras MooTools brings to the table are nice, but YAGNI.
It's not about best, it's about satisficing -- finding the adequate solution to the problem at hand. jQuery is easy to use, its primary aim is DOM manipulation. Since 95% of the people picking up javascript are doing so just to manipulate the DOM, there's no point in going through the longer MooTools learning curve. MooTools simply doesn't bring anything to the table for them that jQuery doesn't deliver with less effort.
MooTools demands more from you before you use it, jQuery lets you throw something together quickly. If you start writing large, heavy-duty js apps, you might run into some of the drawbacks of that approach, but again 95% of the folks writing js don't do that, so those things don't matter to them. They use a server-side language for the heavy-lifting and javascript for the DOM.
For that matter, they may not matter to your team, either. To take you through the lists, point by point (jQuery first):
Large community of supporters -- only slightly relevant to the project. Of more relevance to the team personally, because it speaks to life after you. If misfortune strikes (please, God, no) and your firm is gone, jQuery gets them more jobs than MooTools.
Plugin Repository -- very relevant, as it helps keep from reinventing the wheel.
Integration with Microsoft's ASP.NET and VisualStudio -- very relevant if you're a .NET shop. In fact, this alone should be the reason to switch if you do .NET.
Used by Microsoft, Google and others -- who cares?
Now for the MooTools list:
Object Oriented Framework with Classic OOP emulation for JS -- irrelevant, unless the nature of your projects makes that a plus. I don't know what you're building, but for web shops, this is only rarely relevant. Most web shops don't have enough code to make this a plus.
Extended native objects -- again irrelevant for most web shops
Higher consistency between browsers for native functions support. -- Relevant
More easy code reuse -- This conflicts a little with the jQuery advantage of a large repository. A large repository by itself speaks to reusing code. I suspect you're using a narrow definition of code reuse, here, that may not be relevant. I've reused a lot of the jQuery code I've built, as well as MT code.
Used by The World Wide Web Consortium, Palm and others. -- Irrelevant. The only relevance about who else is using what is if you're wanting a job there. There's more relevance in how many shops use it than in any particular shop using it.
There is no One True Way to approach javascript coding. Get your bias out of the way, and sit down with your team and get their bias out of the way as well. Talk turkey about the specific types of projects you're undertaking (and want to undertake) and the strengths of each library as applied to those cases. (How they might handle other cases doesn't matter, because those other cases don't exist.) You should arrive at a consensus from that.
(YAGNI = You Ain't Gonna Need It, if I need to explain it.)

I choose to use jQuery as our default UI library precisely because it does not extend or otherwise monkeypatch native objects, unlike prototype.js or mootools. Kick in the documentation angle and there really is no question as to which framework to use.

You kinda say it yourself:
Given that, it seems that MooTools does everything jQuery does and more (some things I cannot do in jQuery and I can in MooTools) but jQuery has a smaller learning curve.
Most of the extra stuff that MooTools does is stuff that we just don't need.
As you say yourself jQuery is easier to learn, which is actually more important for most people when choosing a framework.

What I DON'T need in JavaScript is definetely OOP and some ugly object emulation.
Last time I checked MooTools (maybe 1,5 years ago :-), it had browser incompatibilities with manipulating multiple select.
So jQuery is completely looks OK to me.

Not only is jQuery a nice library, but its creator, John Resig, also has some street cred as the author of Pro Javascript Techniques.
We have 2-3 copies of this book around our office.
jQuery is small (intentionally so) but can have functionality added to it through plugins.

The thing that made my experience with mootools a rather unpleasant one was the documentation and the stability of the API:
I simply wasn't able to find a documentation that related to the mootools-Version in use. Won't be that much of a problem if the API defined was stable. But due to some functions that disappeared in the newer Version (a ChangeLog was found after hours of searching) a migration wasn't possible either. After that, mootools was out of the race for me.
Like many others, I don't want to introduce class-based OOP into simple user-interface manipulations. Thats what I use jQuery for: not so complicated user-interface stuff.
When I have to build rich browser-side applications, I'd always switch to the big solutions (ExtJS, YUI, qooxdoo) that offer a variety of ready to use widgets.

Larger User Community and more wide-spread adoption makes a big difference when comparing tools/libraries that offer similar functionality and concepts. Larger community means more support, more examples, more good ideas, and more reusable code snippets, which is especially important when you're working on a rare scenario -- more likely someone else has encountered it before.
Secondly, in benchmarks I've seen, jQuery is faster than MooTools.
I also really like their emphasis on keeping a small core and adding functionality through plugins. Prevents the core library from getting really big and unwieldy.
I've never used MooTools personally but I have no doubt that its a fantastic library that offers some acceptable equivalent to most any jQuery feature or concept, but point #1 takes the cake for me.

Another reason: It's easier to sell jquery to management. Doing internal, asp.net based developement in a corporate environment the magic words are "it's supported by Visual Studio".

For one thing, that's not all it does. There are quite a few other features as well. For another, not everyone uses it. But I don't want to interrupt a good rant.

I have to second a lot of the answers...great documentation and community support is crucial. I used to hate js programming and would avoid it like the plauge, but now I've completely embraced it because of jquery and the quick learning curve.
It's not always about who has the best technology!

Mootools, does not function properly or does not function at all when using jquery prototype etc. Agreed there is absolutely no reason to use them simultaneously, but once in a while they do land up on the same page (ex. plugins, slideshows, widgets etc) and things stop working.
That in itself is unacceptable. So all props for jquery to not create unnecessary headaches!

Why did people start using fax machines? At a certain point the benefit increases exponentially.

Which Javascript Framework is the simplest and most powerful? [closed]

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I've been using various javascript frameworks including mootools, jquery, prototype and scriptaculous and have found them all good, but difficult to extend to more complex ideas.
If I am going to knuckle down and learn one, which is the simplest to extend and use whilst staying powerful enough to use in a variety of directions?

I propose jQuery.
I'll give you some of the major arguments from the presentation that my team put on yesterday for senior management to convince them of that.
Reasons:
Community acceptance. Look at this graph. It shows searches for "prototype", "yui" and "scriptaculous" growing from 2004 to 2008. Then out of nowhere in 2006 searches fro "jquery" shoot up to double the number of the other libraries. The community is actually converging on a single leading product, and it's jQuery.
jQuery is very very succinct and readable. I conducted an experiment in which I took existing code (selected at random) written in YUI, and tried re-writing it in jQuery. It was 1/4 as long in jQuery. That makes it 4 times as easy to write, and 4 times as easy to maintain.
jQuery integrates well with the rest of the web world. The use of CSS syntax as the key for selecting items is a brilliant trick which helps to meld together the highly diseparate worlds of HTML, CSS and JavaScript.
Documentation: jQuery has excellent documentation, with clear specifications and working examples of every method. It has excellent books (I recommend "jQuery in Action".) The only competitor which matches it is YUI.
Active user community: the Google group which is the main community discussion forum for Prototype has nearly 1000 members. The Google group for jQuery has 10 times as many members. And my personal experience is that the community tends to be helpful.
Easy learning curve. jQuery is easy to learn, even for people with experience as a designer, but no experience in coding.
Performance. Check out this, which is published by mootools. It compares the speed of different frameworks. jQuery is not always the VERY fastest, but it is quite good on every test.
Plays well with others: jQuery's noConflict mode and the core library's small size help it to work well in environments that are already using other libraries.
Designed to make JavaScript usable. Looping is a pain in JavaScript; jQuery works with set objects you almost never need to write the loop. JavaScript's greatest strength is that functions are first-class objects; jQuery makes extensive use of this feature.
Plug-ins. jQuery is designed to make it easy to write plugins. And there is an enormous community of people out there writing plugins. Anything you want is probably out there. Check out things like this or this for visual examples.
I hope you find this convincing!

In my opinion, jQuery is exceptionally powerful and simple. It uses CSS selector syntax to pull back elements and only adds two functions to the global namespace: jQuery() and $(), which is an alias for jQuery().
There are a massive number of plugins available for jQuery to let you do things like create slide shows, accordion controls, rich calendars, etc. The book "jQuery In Action" is a phenomenal companion to the online reference material.
We used it on my last project to create a fairly rich scheduling tool and we liked it so much, we're encouraging it's adoption throughout our consulting company as the defacto standard for all JavaScript use. You can check out the results at http://www.stanleysteemer.com

See also (other related questions):
Comparison of Javascript libraries
What JavaScript library would you choose for a new project and why?
What is the single most useful general purpose javascript library for rich internet apps?
Which JavaScript framework is best for web development?
Which JavaScript library is recommended for neat UI effects?
What is the best lightweight javascript framework?
Any good AJAX framework for Google App Engine apps?

jQuery is my favorite

Prototype. Is simple, unobtrusive, and makes your javascript code look cleaner than ever.
It has a wonderful user group, where you can get your questions answered almost immediately

Another vote for jQuery. It's small, focussed, and yet very powerful. It's also reasonable well documented, by the (generally awful) standards of JS libraries.
It's also very easy to extend, once you get your head around the syntax.

NOTE: This answer was pre-Angular/Ember/etc. so addresses an outdated issue.
I teach this stuff, and really had little choice but to home in on JQuery, since the majority in the industry has already 'chosen' it (not always a good reason, I know), but also because - for students that already know some CSS - the entry point is lower.
I've also used Mootools (my second choice), but a colleague convinced my to switch to JQuery with the 'programmability' argument - I find it cleaner to code with and understand. The JQuery community, online documentation, free online books and third-party sites help, too.