I am likely to be part of the teaching team for the web programming course at my University next semester and I was wondering what kind of Javascript assignment to hand out to the students. The course is not an introductory one from a programming perspective.
It is assumed that the students are familiar with OOP, data structures and algorithms, functional programming concepts and working knowledge of networking protocols (HTTP included). This is the first course in which they come in contact with JavaScript
I was thinking to give out something framework-specific (using jQuery perhaps) that involves DOM traversal, some animations and AJAX. The three questions I have in mind are:
should they use a framework or should I have them write vanilla JavaScript?
should I focus more on the functional programming part and on the prototypal inheritance part (more on the language than on working with the DOM)?
how do I automate testing for this? It's better if they have a clear idea on how they will be evaluated. Also, automated testing ensures objectivity and saves me time :).
Outcome
I made them do Tic Tac Toe as a jQuery plugin and the results were mostly satisfactory (70% of the students submitted, generally the submissions were ok).
To prevent copying code from the net, I thought out an API which they had to implement. At least, they'd have to understand the code they found on the net before copy&pasting it into the methods :).
I used QUnit for automated testing, but I also tested each assignment manually because this was the first JavaScript assignment they'd had and I wanted to give relevant feedback.
Thank you all for your ideas, they all helped a lot.
Cheers,
Alex
I think its useful for the students to know fundamentals about the language before working with frameworks. They need to know about JS Scopes, closures, prototypes, the memory model, and everything that makes JS unique.
After that, introduce them to frameworks and the DOM. They'll appreciate them much more since they'll be able to understand the implementation.
As for testing, automated testing might be easy if you have them generate a DOM that you can walk and validate. Mozilla might be able to help you out, esp with JSUnit. You can find info here
I always like the idea of making games to learn new programming concepts. You get a well-defined problem domain that's as simple or complex as you need it, and it's usually more interesting and fun to implement than other problems.
When I wanted to learn Ajax programming I used jQuery and Java server-side to implement the game of chess. It was a fun project, but pretty complicated (at least for me, but I'm primarily a server side programmer). I think something like Tic-Tac-Toe would be substantially simpler, and might be a good idea for a project assignment.
As for the 3 questions:
If this is the only JavaScript assignment, then I'd probably use vanilla instead of jQuery. But if they have a chance to do some assignments before this, I'd consider jQuery, because it just makes JavaScript so much less annoying, and it's also good to know jQuery for future employment possibilities.
I'd place an equal emphasis on both the language and the DOM, because the primary purpose of the language IS to work on the DOM, and the DOM does take some getting used to.
I think Selenium might work for the testing you're trying to do. JsUnit could also be used for unit testing the individual methods.
Start off with vanilla JavaScript to learn the basics. You don't want to create a group that relies on any particular framework that wouldn't know how to do things without it.
I would most definitely have them write vanilla JavaScript. It will encourage all students to better understand the abstractions that frameworks/libraries provide in particular environments i.e. for the most part, in the browser working with the DOM.
I highly recommend having a good text for the course. Object Oriented JavaScript by Stoyan Stefanov is in my mind a great text for learning the language, including some of the topics that many people have difficulty with (prototypes, objects, closures, inheritance, etc). I've read numerous JavaScript books and feel that this particular text best balances the core of the language and it's application in the modern client-side development realm.
You may then want to look at dissecting certain pieces of the source of a particular JavaScript library to gain insight into patterns and practices used in a real-world scenario.
I would have them write vanilla javascript AND also learn how to use jQuery. jQuery is javascript after all, and they need a working knowledge of the language anyway. They'll also need to become SWAT (skills with advanced tools), and I believe anyone not using one of the JS frameworks (or at least their own!) in today's environment is at a serious disadvantage.
See answer 1. I'd teach them about prototypal inheritance in vanilla JS, and about DOM manipulation in jQuery.
Automated testing could be achieved in several ways. 1: produce the correct output given some sample code to start with for the parts that deal with learning JS. 2: for the parts that deal with jQuery, you could provide a reference image for how you expect the result to look, provide an original document, and have them recreate the reference image using jQuery manipulation... sort of like the ACID tests http://acid3.acidtests.org/
Should they use a framework or should I have them write vanilla JavaScript?
To me, it is overwhelmingly import that people new to the language start with the language proper, not modified versions or advanced/fancy libraries that do a lot of the work for you. Besides, if you're starting off not working with the DOM, then you're not getting much benefit from using almost any library, as the bulk of most JavaScript libraries has to do with handling the DOM. Also, it's easier to spot "bad" or ill-performant code when teaching and learning in a "vanilla" environment since you don't have libraries abstracting away the nitty-gritty.
Should I focus more on the functional programming part and on the prototypal inheritance part (more on the language than on working with the DOM)?
Yes! On one hand, the DOM is not not that big of a deal; yet it is also the core of what JavaScript is used to interact with. For starters, I suggest that if you're going to be using a browser environment, you should initially avoid the DOM by using Firebug's console.* methods for output so that you can focus on the "functional programming part and on the prototypal inheritance" and other core concepts. After these core concepts have been covered, then start introducing the DOM. It's best to introduce the DOM later as time will need to be dedicated to cross-browser compatibility, which will only confuse the subject if you are trying to teach the core concepts in tandem.
How do I automate testing for this? It's better if they have a clear idea on how they will be evaluated. Also, automated testing ensures objectivity and saves me time :).
Before (and after) the DOM is introduced, you could use something like JSUnit. Also, see this question: Automated Unit Testing with JavaScript. Once you introduce the DOM, you may want to have the students generate a document that you can walk and validate as SB suggested.
Related
I have been a user of jQuery (and some of its minor plugins) for a while. The Javascript code I've developed over the years could be described best as... messy. It used a ton of global variables and functions here and there, didn't use standard ways of organizing the code, nor any design patterns whatsoever.
I am currently building the new version of a website, and I have completed doing the backend with PEAR::MDB2 and Smarty templates. The rest is just homebrew PHP with some classes.
Now I am at the point where I'll add the Javascript layer on top of the website to improve the user-friendliness of some features. (while making sure everything degrades gracefully) I want to write better, cleaner, more organized Javascript than I used to, so I did a little research. I read Stefanov's Object-Oriented Javascript to have a better grasp on some concepts I knew only loosely about (prototypes, constructors, etc.) as well. Now I'm stuck at a point where I wonder which Javascript frameworks I should use, and how to organize it all.
After conducting my research, I understood Cappuccino & Objective-J, and Sproutcore were not what I was looking for. To quote Cappucino's about page:
Cappuccino is not designed for building web sites, or making existing sites more "dynamic". We think these goals are too far removed from those of application development to be served well by a single framework. Projects like Prototype and jQuery are excellent at those tasks
So there's that. Then I found out about Coffee Script, which is more of a one-to-one "compiler" and wouldn't help me with the actual organization of my code.
I also stumbled on some articles that give guidelines:
Using Inheritance Patterns to Organize Large jQuery Applications
A JavaScript Module Pattern
I also found out about Backbone.js, Shoestring, JavaScriptMVC, Google Loader, jQuery Tools, jQuery UI. I don't really know what to do of all this... The things I know:
I don't want to invest too much time in learning something too complex, I want to keep things simple and flexible as much as possible (that is why I don't use Symfony on the backend, for example), yet clean and organized.
I want to use jQuery, the question is, what should I use with it? (that is compatible too)
Right now, I'd use jQuery and jQuery Tools and "organize" all that in a simple namespace/object literal with simple properties and methods and also, since the site is localized, I just plan on using the simple vsprintf (as I do on the backend) with key:value pairs loaded from an object literal provided by the backend. JavaScriptMVC seems interesting, but I fear it would bring way too much complexity for a project that is fairly small sized. That is where I need your advice! Thank you very much in advance.
Ok, my attempt at an answer:
There is no 'best' to way to do it. You now know what's there and I think you might have a preference for yourself for what you want. In that case, pick a framework and learn it inside-out. (sorry to burst your bubble, but each framework has a learning curve, some steep, some very easy, but in the end to use it well you have to invest in it. Just do it, you won't be sorry).
You of course have an preference for clean code, so you might take some considerations into account. You also say you have a preference for jQuery, which is fine, but there are some limitations (as also pointed out in the link provided by eskimoblood).
There are some nice lectures / and tutorials with advice on how to structure your code in jQuery:
How to manage large jquery apps
On Large jQuery apps
Essential Javascript and jQuery patterns (free ebook)
Some style guides:
Jquery core UI Styleguide
Google Closure Javascript Style Guide
Tools for checking your code
JSLint
JSHint (a more forgiving/practical fork)
Closure Linter (haven't tried it yet, but intend to)
Standard works (javascript)
Everything by Douglas Crockford
Quirksmode
There might be more.. perhaps more people can contribute, but I also think that you've almost reached the end of what you can learn before getting your hands dirty. Many of these guides are written in a very generic way, but the interesting thing is that javascript is called upon in many specific situations. It might be useful to just post some of the code that you regard as "messy" and we can help you figure out how to do it better. Good luck!
You should watch the video and read the links in this article and then you should ask yourself again if jquery is the right tool. Maybe you will use dojo, that is much better for larger projects or you take a look at backbone and where you can stay with jquery. After all both of them are more "javascriptish" then something like sproutcore, cappuciono or even GWT. And also much easier to understand when you come from jquery.
One framework that is to consider is definitely ReactJS from Facebook. This framework is pretty slick in many ways.
First thing you have to know is that it is a view framework. It can be used server-side to do the pre-rendering of pages, but it really shines on client side. Since it's a view framework, it can be used with backbone or any other "back-front"-end framework.
One of the main point of React is its rapidity. It keeps a virtual DOM in memory and virtualize all the webpages events. So the virtuals event are used to keep events browser agnostics.
The virtual DOM kind of make programming a dynamic site as if you were programming an old static website. You can just shoot the whole HTML to render to the view engine (as if you were "re-rendering" the whole page) and it will manage the DOM operations. It does a diff between the new virtual DOM and the current virtual DOM and only inserts nodes that needs to be inserted. This way you reduce the number of DOM ops and thus increase your render speed by a lot.
A good place to start is this tutorial which shows how to use "Flux" (the web flow designed by Facebook for its site) in order to realize a Todo application!
I'm curious what's the view on "things that compile into javascript" e.g. GWT, Script# and WebSharper and their like. These seem to be fairly niche components aimed at allowing folks to write javascript without writing javascript.
Personally I'm comfortable writing javascript (using JQuery/Prototype/ExtJS or some other such library) and view things like GWT these as needless abstractions that may end up limiting what a developer needs to accomplish or best-case providing a very long-winded workaround. In some cases you still end up writing javascript e.g. JSNI.
Worse still if you don't know what's going on under the covers you run the risk of unintended consequences. E.g. how do you know GWT is creating closures and managing namespaces correctly?
I'm curious to hear others' opinions. Is this where web programming is headed?
Should JavaScript be avoided in favor of X? By all means!
I will start with a disclaimer: my answer is very biased as I am on the WebSharper developer team. The reason I am on this team in the first place is that I found myself a complete failure in writing pure JavaScript, and then suggested to my company that we try and write a compiler from our favorite language, F#, to JavaScript.
For me, JavaScript is the portable assembly of the web, fulfilling the same role as C does in the rest of the world. It is portable, widely used, and it will stay. But I do not want to write JavaScript, no more than I want to write assembly. The reasons that I do not want to use JavaScript as a language include:
There is no static analysis, it does not even check if functions are called with the right number of arguments. Typos bite!
There is no or a very limited concept of libraries, namespaces, modules, classes, therefore every framework invents their own (a similar situation to that of R5RS Scheme).
The tooling (code editors, debuggers, profilers) is rather poor, and most of it because of (1) and (2): JavaScript is not amenable to static analysis.
There is no or a very limited standard library.
There are many rough edges and a bias to using mutation. JavaScript is a poorly designed language even in the untyped family (I prefer Scheme).
We are trying to address all of these issues in WebSharper. For example, WebSharper in Visual Studio has code completion, even when it exposes third-party JavaScript APIs, like Ext Js. But whether we have or will succeed or fail is not really the point. The point is that it is possible, and, I would hope, very desirable to address these issues.
Worse still if you don't know what's
going on under the covers you run the
risk of unintended consequences. E.g.
how do you know GWT is creating
closures and managing namespaces
correctly?
This is just about writing the compiler the right way. WebSharper, for instance, maps F# lambdas to JavaScript lambdas in a 1-1 manner (in fact, it never introduces a lambda). I would perhaps accept your argument if you mentioned that, say, WebSharper is not yet mature and tested enough and therefore you are hesitant to trust it. But then GWT has been around for a while and should produce correct code.
The bottom line is that strongly typed languages are strictly better than untyped languages - you can easily write untyped code in them if you need to, but you have the option of using the type-checker, which is the programmer's spell-checker. Why wouldn't you? A refusal to do so sounds a bit luddite to me.
Although, I don't personally favor one style over another, I don't think that abstraction from Javascript is the only benefit that these frameworks bring to the table. Surely, in abstracting the entire language, there will be things that become impossible that were previously possible, and vice-versa. The decision to go with a framework such as GWT over writing vanilla JavaScript depends on many factors.
Making this a discussion of JavaScript vs language X is fruitless as each language has its strengths and weaknesses. Instead, do an objective cost-benefit analysis on what is to be gained or lost by going with such a framework, and that can only be done by you and not the SO community unfortunately.
The issue of not knowing what goes on under the hood applies to JavaScript just as much as it does to any translated source. How many people do you think would know exactly what is going on in jQuery when they try to do a comparison such as $("p") == $("p") and get back false as a result. This is not a hypothetical situation and there are several questions on SO regarding the same. It takes time to learn a language or framework, and given sufficient time, developers could just as well understand the compiled source of these frameworks.
Another related aspect to the above question is of trust. We continuously build higher level abstractions upon lower level abstractions, and rely on the fact that the lower level stuff is supposed to work as expected. What was the last time you dug down into the compiled binary of a C++ or Java program just to ensure that it worked correctly? We don't because we trust the compiler.
Moreover, when using such a framework, there is no shame in falling back to JavaScript using JSNI, for example. It's all about solving the problem in the best possible manner with the tools at hand. There is nothing sacred about JavaScript, or Java, or C#, or Ruby, etc. They are all tools for solving problems, and while it may be a barrier for you, it might be a real time-saver and advantageous to someone else.
As for where I think web programming is headed, there are many interesting trends that I think or rather hope will succeed such as JavaScript on the server side. It solves very real problems for me at least in that we can avoid code duplication easily in a web application. Same validations, logic, etc. can be shared on the client and server sides. It also allows for writing a simple (de)serialization mechanism so RPC or RMI communication becomes possible very easily. I mean it would be really nice to be able to write:
account.debit(200);
on the client side, instead of:
$.ajax({
url: "/account",
data: { amount: 200 },
success: function(data) {
..
}
error: function() {
..
}
});
Finally, it's great that we have all this diversity in frameworks and solutions for building web applications as the next generation of solutions can learn from the failures of each and focus on their successes to build even better, faster, and more awesome tools.
I have three big practical issues I have with websharper and other compilers that claim to avoid the pain of Javascript.
If you won’t know Javascript well you can’t understand most of the examples on the web of using the DOM/ExtJs etc., so you have to learn Javascript whatever. (For the some reason all F# programmers must be able to at least read C# or VB.NET otherwise they cannot access most information about the .net framework)
On any web project you need a few web experts that know the DOM and CSS inside out; would such a person be willing to work with F# rather than Javascript?
Being tied into the provider of the compiler, will they be about in 5 years’ time; I want full open source or the tools to be supported by Microsoft.
The 4 big positives I see with these frameworks are:
Shareing code between the server/client
Having fewer languages a programmer needs to know (javascript is a real pain as it looks like Jave/C# but is not anything like them)
The average quality of a F# programmer is a lot better than a jscript programmer.
My opinion for what it's worth is that every framework has its pros/cons and a project team should evaluate their use cases before including one. To me any framework is just a tool to be used to solve a problem, and you should pick the best one for the job.
I prefer to stick to pure JavaScript solutions myself, but that being said I can think of a few cases where GWT would be helpful.
GWT would allow a team to share code between the server/client, reducing the need to write the same code twice (JS and Java). Or if someone was porting a Java client to a web UI, they may find it easier to stick to GWT ( of course then again it may make it harder :-) ).
I know this is a gross over-simplification, because there are many other things that frameworks like GWT offer, but here is how I view it: if you like JavaScript, write JavaScript; if you don't, use GWT or Cappuccino or whatever.
The reason people use frameworks like GWT is not necessarily the abstraction that they give--you can have that with JavaScript frameworks like ExtJS--but rather the fact that they allow you to write web applications in something other than JavaScript. If I were a Java programmer who wanted to write a web application, I would use GWT because I would not have to learn a new language.
It's all preference, really. I prefer to write JavaScript, but many people don't.
I'm pretty efficient in jQuery, having implementing it in several projects for my company. However, I found myself a little lost when reading stuff like node.js.
Do I have to go back to basics and learn the JavaScript language or should I just stick with jQuery?
One more thing I would like to ask: Does coding in plain JavaScript increase performance compared to coding with jQuery? For my own experience, coding heavy, complex combination of animation in jQuery always seems to take up large amount of the computer memory.
You should understand what's going on, to a degree. It doesn't hurt to know what's underneath, but sometimes that's not optimal to know everything either, for example: is .innerHTML consistent? Not completely, e.g. <select> in IE. Does that mean you need to know every inconsistency? Not if you're letting jQuery handle it.
People say you need to understand JavaScript before jQuery, let me say I agree, however there are limits to that though, you don't necessarily need to know every quirk and inconsistency between browsers for example, that's why we use an abstraction layer.
To me, this is no different than saying you need to learn assembly before C#, should you know what's happening, how memory is referenced, what a pointer is? I think so, do you need to know every detail? Probably not. We would never progress if every new programmer goes through learning every layer beneath, this is why math theorems build upon others known to be true, same concept.
You should be able to trust your abstraction layer. Is this always true? unfortunately not, but jQuery does a pretty good job at being as consistent as possible and always improving. More importantly, the community does a good job of making the inconsistencies known.
Edit: Let me caveat everything above by saying if you can learn what's underneath do so (this applies to most any abstraction in my book, not just JavaScript), it will help you program better and more efficiently. If you know what's going on under the covers, you can more optimally take advantage of it.
It's a lot like apples and oranges, actually. jQuery is awesome library but it focuses on DOM manipulations. It does not help you much with general coding, prototype inheritance, closures, data types and other important stuff you have to deal with when programming.
node.js have nothing to do with DOM, so it is very much orthogonal to jQuery, no wonder you have trouble understanding it.
Note, however, that knowledge of JavaScript won't necessarily mean you'll be efficient with every JavaScript library out there. Each library makes kind of a superset of a language, a domain specific language to help with specific task that library was built to solve. You will always have to learn that DSL first to be efficient but it'll be easier to understand internals of any given library if you know JavaScript well.
If you are only interested in application programming (web sites and applications) then jQuery is more than adequate. If you want to develop a JavaScript framework or library, then proficient knowledge of the JavaScript language is necessary.
Does being good in jQuery imply being good in JavaScript?
No. I strongly suggest you learn the basics and then some.
jQuery is just a library. While productive, being well versed in the functionality that a library provides is not the same as being good at the language in which that library is written in.
I'm not saying that you need to know that all bitwise operations are converted to signed 32-bit integers in big-endian order, but you do need to know about core concepts like closures, how to properly attach event handlers, and the basic concepts of asynchronous/event oriented programming.
What if you were to change jobs to a company that uses ExtJs instead of jQuery? Understanding the core concepts of the language will make these sorts of transitions non-problematic.
Another thing to consider is that for every library, there is always a task that it doesn't support. Being reliant on a library to always do the heavy lifting will eventually bite you in the hind parts.
Does coding in plain JavaScript increase performance compared to coding with jQuery?
Libraries typically aim to be as generic as possible for the area of use they are targeting. Because of this, inefficiencies may occur in some scenarios that could be otherwise optimized outside of the library.
It all depends on how adept you are at JavaScript, algorithm selection/creation/analysis, and programming in general. When you start concerning yourself with being as high performing as possible, you really need to be able to get down to the finer details of a language. "Being good" at jQuery, or any library for that matter, will likely not help you with this (unless you're looking under the hood and implementing their techniques in a manner that is specific to your scenario).
jQuery is just a list of (very) useful functions, written in JavaScript.
You are just using the library without understanding what's behind it
and how things work. Most of the time you will only need jQuery for maybe 20%-40%
of your code, and the rest will be pure JavaScript, so I encourage you to learn the
basics. These are good places to start with:
http://www.w3schools.com/jsref
http://howtonode.org/what-is-this
http://net.tutsplus.com/tutorials/javascript-ajax/the-basics-of-object-oriented-javascript/
http://ejohn.org/apps/learn/
I'm a bit ambiguous on this. Knowing real deep JavaScript is a great art - I am always in awed silence when one of our resident deep JavaScript experts comes to the table. However, not everyone needs that kind of deep knowledge - if you're focused on building interfaces, knowing one of the frameworks well may be everything you ever need, with very few edge cases.
On the other hand, knowing at least the basics of how JavaScript works under the hood can only be beneficial. If you feel driven to take a look into it, I'd say do it. You don't have to become a total guru in fundamental JavaScript but having a basic idea of how data is handled internally, how events are processed by the browser, how memory is managed, etc. is a good thing.
Not necessarily, it is like saying like being good in Java is same being good in byte code since it is using the byte code.
jQuery is an abstraction layer for JavaScript, and for this reason most of the time you will be doing it all in jQuery rather than raw JavaScript. However, it is always a good idea to have some JavaScript knowledge at least for the required parts.
For this reason, if you see any jQuery book out there, most of them have a chapter or index regarding the "Basics Of JavaScript" or "JavaScript for jQuery".
I learnt HTML/CSS a good few years back, then PHP a little later. I've recently become interesting in web development again, just started playing with frameworks like Django and RoR. I'm curious as to how much time/effort I should spend learning straight JS before looking at frameworks. I've been reading through a let of articles called Mastering AJAX by Brett McLaughlin which seems quite good, but I'm seeing a lot of stuff (such as cross browser compatibility - even for things like XMLHttpRequest) coming up which look like they would be non-issues if using a framework.
So, should I keep reading through these articles and try to build stuff using basic JS, or should I just start looking into jQuery and the like?
Also, I've been watching a few videos regarding GWT from Google I/O. I've been learning Java over the last year, built a few medium sized apps in it. I'm wondering if GWT is something that's worth going straight to, along with gQuery?
Starting with the basics of JavaScript is a good idea, IMHO.
Read JavaScript: The Good Parts, by Douglas Crockford. Very, very good book.
You should also check out Douglas Crockford's web site.
I also had to come back here and mention this in an update:
Douglas Crockford presented an illuminating talk about JavaScript - past, present, future - at the Microsoft MIX10 conference earlier this year. You'll find the full video for Crockford's talk at Microsoft MIX10 - The Tale of JavaScript. I Mean ECMAScript.
No.
Just as when you are learning to program you are taught first C/Pascal then Java/C++ and finally Python/Ruby/Smalltalk/Lisp, and when learning any language you start with simple language constructs, you should first learn ECMAScript, then learn DOM and finally frameworks.
Why? Because you'll have a deeper understanding of the language, and will be able to debug things that might seem odd unless you've got that learning experience.
If you are a seasoned developer, you can speed up each phase, but don't skip them, or you will have problems due to not fully understanding the small oddities.
Javascript is an interesting and fun language, but can act rather odd at times (Date has bitten me a couple of times in the ass).
Use frameworks to avoid repetitive tasks and to simplify your code, but not as a starting point. Simplicity is a final goal, not the starting point, and frameworks are for that, simplicity, not for learning a language. Frameworks are intended for simplifying things for experienced developers.
Learning the differences between browsers (DOM implementations) will allow you to debug your framework. That is priceless.
I've been learning Java over the last
year...
Javascript is not Java. Never was never will.
Even if you can compile to Javascript from Java, it's still a framework, don't jump into it unless you already know what you are doing.
I think "both." Mix it up. Play around with a framework. You'll get stuck when you try to do something real, so you'll pick up some JavaScript to figure it out.
A lot of the good jQuery books teach you JavaScript along the way.
This is one of the best videos for beginner javascript developers that understand how to program in other languages:
It's a talk the John Resig did last year at Northeastern, most of it is devoted to talking about core javascript, then the last quarter of the talk jumps into jQuery:
http://video.google.com/videoplay?docid=-7485992465859932389&ei=jhZUSu73OpfSrQLgyYV3&q=john+resig&hl=en
It's actually a really interesting tech talk and presentation since he does live examples and Resig is pretty good at presenting.
Like others in this question, I also highly recommend reading Javascript: The Good Parts for a better understanding.
Yes, jumping straight to framework-based programming instead of DOM is a good idea.
I started doing JS before any major frameworks like jQuery came along, and was reluctant to switch at first, but when I first started using jQuery, it felt so good to be able to write selectors and stuff and not have to worry about cross-browser compatibility.
However, there are some areas of JS where frameworks wouldn't be available. One of them is in userscripting, where you have to make your script work on a site you don't control. Another such one is the use of JavaScript in applications such as XUL.
Overall, I suggest you start with some trivial JS applications, then switch to jQuery instead of going on to the complex topic of DOM.
What makes you think that the frameworks are the good stuff and the JavaScript is not?
If you ask me, I will say that JavaScript is a real fun language and you should learn it first. JavaScript has received bad rap because it was mainly used for browser scripting and those browsers were buggy making people think that JavaScript sucks.
Crockford says that JavaScript is the world's most misunderstood language.
If your prior experience is with PHP (or any non functional language for that matter), the concept of 'first class functions' will really give you an 'aha' moment. 'Closure' will be another tool which will simplify your code and will make you wonder why all languages don't have it. Prototype inheritance will show you that there are alternatives to OOP. I would definitely suggest that you learn JavaScript first before you jump to any frameworks. I must add that you will also have to learn the concepts (first class functions/closure/prototype inheritance), to use any JS framework efficiently as all frameworks exploit the features of JavaScript.
To learn JavaScript, get Crockford's 'JavaScript, The Good Parts' book and try to learn the language using a standards compliant browser (say Firefox [with FireBug], Safari, Chrome) without focusing on DOM manipulation. This presentation by Simon Wilson is also good.
Once you have a good feel for the language, move on to the next step i.e. manipulating the DOM. I would personally suggest that you try to do some DOM manipulation using bare bone JavaScript to get better understanding of the DOM and the pain points involved. [E.g., when I attach a method to onClick of event, 'this' doesn't refer to what I think it refers to?]
After you have suffered a little bit of pain by doing DOM manipulation by hand, move on to a JavaScript framework which removes all the pain and makes JavaScript fun again. Personally, I would highly recommend jQuery over other frameworks.
And if you have any questions while on your JavaScript journey, you can always ask them on SO! :) Good luck.
I wouldn't touch any framework in any language until I have good basic understanding of underlying technology. Worth type of coder is one that uses tool without a knowledge.
JavaScript has somewhat sad history but in its latest incarnation it's surprisingly powerful and even fascinating language. I say - learn it well, then use whatever framework suits your current needs
It depends on where you want to invest your time. Ideally, we're all expert in assembly language, but that's not realistic or practical. We have to pick our battles. Then generally we attack each other for picking the wrong battle, which we call "cargo cult coding."
Personally, out of all the things I could spend a lot of time banging my head against, the intricacies of cross-platform JavaScript seemed less interesting and rewarding than other choices, so I decided to jump straight to jQuery. I'm happy with how it worked out.
I had the same background as you. After 6 months of MooTools I found out that mootools was indirectly teaching me "vanilla" javascript.
I've heard people say that mootools feels more like plain ol' javascript than jquery (after all, jquery's tagline is "jQuery is designed to change the way that you write JavaScript.").
I'd recommend starting with a framework. Plenty of the best javascript developers use frameworks. Once you're comfortable there you'll likely be able to pick up the others frameworks and plain ol' javascript quite readily.
We have a CMS built on Java and it has Mozilla Rhino for the server side JS. At the moment the JS code base is small but growing. Before it is too late and code has become a horrible mess I want to introduce some best practices and coding style.
Obviously the name space control is pretty important. But how about other best practices - especially for Java programmers?
Here's some tips from the front lines:
Like Java, use docblocks in Doxygen/JsDoc style for functions
Unit test. Personally like JsTestDriver, as it can be executed automatically from CI server too.
Use JSLint. It will nitpick about bad code
Consider using Google Closure Compiler. It will nitpick about code like JSLint, but it can be helpful for spotting poor doc blocks etc.
Make sure everyone on your team understands how closures work. Otherwise it'll lead to headaches
As you mention, namespaces are important especially if you want your code to work nice with other JS libraries (var myns = myns || {};)
Personally I find using a library which provides OOP helpers like classes etc. helpful. You could use prototypal inheritance but it's often a bit trickier that way.
As Douglas Crockford likes to say, JavaScript is the worlds most misunderstood programming language. Though many people don't know it, there is a right way to code in JavaScript. I have no doubt that if you let Java developers start coding before understanding how to write good JavaScript you will run into serious trouble.
The first thing to do would be to make sure everyone has read Mozilla's excellent article, A re-introduction to JavaScript (https://developer.mozilla.org/en-US/docs/Web/JavaScript/A_re-introduction_to_JavaScript). One of the biggest problems with JavaScript is that there are many ways to do most common tasks, and this article should get people on the same page. Another essential reference is Douglas Crockford's work, including JavaScript: The Good Parts.
One other thing that gets a lot of Java/C++ programmers is that JavaScript uses function scope NOT block scope. This can cause some very tricky problems. There's a great article about this issue at A List Apart called Binding in JavaScript.
To summarize the major issues talked about in the above resources, the most crucial differences to learn are
how to write object oriented code using prototypal inheritance (vs.class based inheritance)
how to use closures and lambdas
how to utilize the power of dynamic objects
how to write function-scoped code
Since you have a JS engine in Java, make it a habit to write unit tests for your JS code. Select a coding style and apply it vigorously. If possible, use tools to check that the code submits to the coding style.