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I have some procedural javascript code that I have written for an open-source application and I'd Like to refactor it into OOP and since I have very little experience with javascript frameworks I have trouble finding a one suitable for my needs, though I haven't tried anything yet, I just read about AngularJS, Backbone.js and Knockout.
I want to structure the code, because, at the moment, there's a mess, global variables and functions scattered around.
I have to mention that all the business logic is handled at the server level, so the client-side code handles just the UI using the data it receives or requests from the server.
The code can be found here:
https://github.com/paullik/webchat/blob/asp.net/webchat/Static/Js/chat.js
Do you have any suggestions?
Object-Oriented JavaScript is not necessarily the answer to all your
problems.
My advice is to be careful the choice you pick on this topic.
In practice, OO-JS can add more complexity to your code for the sake of trying to be more like traditional object-oriented languages. As you probably know, JS is unique.
It is important to know that there are Design Patterns that will structure your code and keep implementation light and flexible.
It is Design Patterns that I see structuring advanced JS
implementations, not OO. To paraphrase Axel Rauchmeyer - "Object
Oriented methodology does not fit into basic JavaScript syntax, it is
a twisted and contorted implementation, and JS is far more expressive
with out it."
The root of this analysis boils down to the fact that JS has no class. In essence, since everything is an object, you already have object-oriented variables and functions. Thus the problem is slightly different than the one found in compiled languages (C/Java).
What Design Patterns are there for JavaScript?
An excellent resource to check is Addy O' Somani and Essential Design Patterns.
He wrote this book on Design Patterns in JavaScript.
But there is more... much more.
A. require.js - There is a way to load modules of JS code in a very impressive way.
These are generally called a module loaders, and are widely considered the future of loading js files since they optimize performance at runtime. yepnope and others exist. Keep this in mind if you are loading more than a few js files. (moved to top by request).
B. MVC - There are dozens of Model View Controller frameworks to help you structure code.
It is a Pattern, but may be unreasonable for your purposes. You mentioned backbone, knockout and angular... Yes. These can do the trick for you, but I would be concerned that they might be 1) high learning-curve, and 2) overkill for your environment.
C. Namespace or Module Pattern. Are probably the most important for your needs.
To solve global variables just wrap them in a namespace and reference that.
These are very good patterns that give rise to module loaders.
D. Closure - You mentioned OO JS. On piece of this that is useful is the notion of closures to provide yourself with... private members. At first this is a cryptic idea, but after you recognize the pattern, it is trivial practice.
E. Custom Events - It becomes very important to not use hard references between objects. Example: AnotherObject.member; This is because it will tightly couple the two objects together and make both of them inflexible to change. To solve this, trigger and listen to events. In traditional Design Patterns this is the Observer. In JS it is called PubSub.
F. The Callback - The callback pattern is what enabled AJAX and it is revolutionizing development in terms of Window 8, Firefox OS, and Node.js - because of something called non-blocking-io. Very important.
Do not be afraid. This is the direction to go for long-term and advanced JavaScript implementations.
Once you recognize the patterns, it is down hill from there.
Hope this helps.
I was full time java developers, now I also work on JavaScript. couple of years back when I started learning JavaScript, first library I tried was jquery like most of the people. But it made my life harder, and after sometime I started writing fairly large JavaScript app. It wasn't coming together for me using jquery. I had huge codebase without much of a structure. It was method blocks updating HTML blocks using selectors.
Then I tried mootools and obliviously as a java developer it appealed to me a lot. And I was able to write managible web apps having huge code base.
As per my understanding Mootools is not considered a preferred way to write JavaScript because it mimic conventional OO over default prototype-based OO language. So now to really understand javascript and desire of walking with the world, i decided to try other approaches, so again I turned back to jquery, and realise that only jquery is not enough. So started looking at current trending frameworks like backbone, spine, ember.js, sprouteCore. Strangly I found that these frameworks at their core tries to mimic conventional OO like mootools only by having constructors and creating a object of class and reusing this class object to create instance objects. So
Am I missing something?
Is mootools way really wrong?
Mootools project is very alive and releases new versions/features, but I don't
see many people talking about it on Internet, also there are no comparisions vs backbone/spine etc.
As per my understanding Mootools is not considered a preferred way to write JavaScript because it mimic conventional OO over default prototype-based OO language.
Where do you get that from? The greatest thing about javascript is that is so loosely typed (see what I did there) - you can write the same thing in a platitude of ways. There are also so many ways to abstract it and repackage it - and this applies from a simple new Array() vs [] to how you structure your app.
If you love JavaScript (or just know it and secretly hate it), you will be fine with MooTools. The API is mostly either native js or ES5 spec or - rarely - an extra utility that also feels 'natural'. The notable exception that stands out is Class. And the fact that you can abstract having to deal with prototypical inheritance by passing an object to a special constructor Type function that returns your instance is ... oh wait. It looks different but what it does pretty much sounds like normal javascript. Only easier -- why wouldn't you prefer that?
A lot is being made these days of the clientside MVC boom and this 'new way of developing apps'. Suddenly, jQuery folks were given the luxury of tap water! I have spoken to a lot of MooTools developers over this and (un)surprisingly discovered that most think MooTools rarely needs anything like that. I tend to agree with them. The only gaping hole is a view controller with templating but there are a fair few solutions.
The thing is, you cannot directly compare a MVC framework with MooTools, it is not the same. At all. You can compare the so called Model constructors vs Classes.
I have now spent a while researching various MVC framework solutions and patterns to see if our new app can be moulded into a 'best practice' shape.
Basically, I tried backbone.js (with and w/o a mootools adapter) and found it awkward to use after MooTools - it felt like a step back. When I say use I don't mean I can't use it but it feels awkward to extend and build on. I am sure it's just down to experience, though, have yet to read all the backbone patterns examples out there.
Typical issue I run into - wanted to have a special Model property that tells it to use localStorage to fetch/save. Not obvious how - examples tend to show you can either route Backbone.sync to one or the other but not both at the same time. I had to actually decorate the function and extend it, keeping the original referenced in case the model did not require localStorage. NOT the best / most obvious pattern to maintain and leaves me dependent on their changes not breaking my code.
In MooTools, I would have just extended my Model class and could have defined a custom Class Mutator property (like Binds or Implements). Done. Write what you know, they say, and not for nothing...
Another issue - it's tightly coupled with data and you cannot reuse models like classes - eg, a User model loads a user and renders through a User Edit view. You then want to create a new customer and suddenly, you cannot reuse the old object that easily and just render the same view but with empty values. I think it will also be down to inexperience on my part or bad architecture.
Ember.js I found slightly more moo-ish as an interface though It did not quite click either. Frankly, backbone was less trouble to setup.
There are other attempts. Composer is one - once again for mootools but it tries too hard to be backbone and is written by people that are relatively new to the framework so I would not call it mature. Knockout etc etc. There's a new one every day, literally.
Garrick Cheung released a framework called Neuro which has huge potential.
I wrote Epitome - a full MVP implementation based upon classes and events and wrapped in AMD modules, feel free to check it out. It also comes with a builder, documentation builder and many little goodies to get you started.
SeanMonstar released Shipyard, which is used by Mozilla Flight Deck - http://seanmonstar.github.com/Shipyard/. Whereas it's not native mootools, it's mootools-ish with mootools class etc - only w/o extending natives, so a great alternative.
BTW, try irc.freenode.net #mootools or the mail list and you will always get a good answer.
Anyway, enough on MVC. The points about MooTools have been made countless of times. Haters will be haters. Those that love it don't look back. If you are a programmer from an OOP background or are looking for something that renders itself well to patterns, do yourself a favour and stick with it. Exciting times are ahead. Roadmap for 1.5: AMD, for 2.0 (aka, Prime) Host object prototyping optional. These have been the two biggest talking-down points in the eyes of critics. No more 'dirty' prototypes so people can get on with using for ... in loops incorrectly on non-objects and without hasOwnProperty checks. Anyway...
Other things to worry about may be of importance. Like, the size of the 'community'. I think having a healthy community is a great thing but even if you look at jquery, the amount of actual contributors vs users is low. The ratio of quality CODE vs good looking effects is bad. The plugins you can use - a lot are not well written or dead and unsupported. When you draw the line, it's a lot less glamorous than you'd think!
I am not saying that mootools or other frameworks don't have these problems. It is fair to say MooTools people and especially the core devs are fairly private and less vocal about what they do. It may send the wrong impressions, I don't know. It certainly is no jQuery.
Ultimately - if you have the resources and the know-how, use what works best and what will scale. There are even these that use coffeescript and swear by it. Who am I to judge...
In the interests of full disclosure - you will find it MUCH harder to find a decent mootools dev when you recruit. Cannot be ignored...
Coming from Java, I'm wondering if a Java best practice applies to JavaScript.
In Java, there's a separation of interface and implementation, and mixing them up is considered a bad practice. By the same token, it is recommended to hide implementation details of your library from end developers.
For example, log4J is one of the most popular logging libraries out there but it is recommended to write code to the slf4j library or the Commons Logging library that "wraps" log4j. This way, if you choose to switch to another logging framework such as logback, you can do so without changing your code. Another reason is that you, as a user of a logging library, how logging is done is none of your concern, as long as you know what logging does.
So back to JavaScript, most non-trivial web applications have their own custom JavaScript libraries, many of which use open source libraries such as jQuery and dojo. If a custom library depends on, say jQuery, not as an extension, but as implementation, do you see the need to add another layer that wraps jQuery and makes it transparent to the rest of JavaScript code?
For example, if you have the foo library that contains all your custom, front-end logic, you'd introduce the bar library that just wraps jQuery. This way, your foo library would use the bar library for jQuery functions, but it is totally oblivious to jQuery. In theory, you could switch to other libraries such as dojo and google web toolkit without having a big impact on the foo library.
Do you see any practical value in this? Overkill?
Although it makes sense from a theoretical standpoint, in practice I'd say it's overkill. If nothing else for these two reasons:
Anything that adds to the size of
the request (or adds more requests)
is bad - in web world, less is more.
If you're using say jQuery, the
chances of you switching to
something like Mootools is (imho) slim to none. From what I've seen, the top libraries each aim to solve different problems (at least in the case of Mootools and jQuery - see this great doc for more info on that). I'd assume that you'd incur a tremendous amount of headache if you were to try to implement a middleware library that could easily switch between the two.
In my experience and being a Java developer myself, sometimes we tend to take the whole "abstraction" layer pattern too far, I've seen implementations where someone decided to completely abstract a certain framework just for the sake of "flexibility" but it ends up making things more complicated and creating more code to maintain.
Bottom line is you should look at it on a case by case basis, for example you wouldn't try to create an abstraction layer on top of struts, or on top of JPA, just in case you then go to a different framework (which I've rarely seen done).
My suggestion is, regardless of the framework you are using, create objects and components that use the framework internally, they should model your problem and be able to interact between them without the need of any specific framework.
Hope this helps.
There are a lot of good answers here, but one thing I don't see mentioned is feature sets. If you try to write a library to wrap the functionality provided by, say, jQuery, but you want to be able to easily swap out for something like prototype, you have a problem. The jQuery library doesn't provide all the features prototype provides, and prototype doesn't provide all the features jQuery provides. On top of that, they both provide their features in radically different ways (prototype extends base objects -- that's damn near impossible to wrap).
In the end, if you tried to wrap these libraries in some code that adds 'abstraction' to try to make them more flexible, you're going to lose 80% of what the frameworks provided. You'll lose the fancy interfaces they provide (jQuery provides an awesome $('selector') function, prototype extends base objects), and you'll also have to decide if you want to leave out features. If a given feature is not provided by both frameworks, you have to either ditch it or reimplement it for the other framework. This is a big can of worms.
The whole problem stems from the fact that Java is a very inflexible language. A library provides functionality, and that's it. In JavaScript, the language itself is insanely flexible, and lets you do lots of crazy things (like writing a library, and assigning it to the $ variable). The ability to do crazy things lets developers of javascript libraries provide some really creative functionality, but it means you can't just find commonalities in libraries and write an abstraction. I think writing javascript well requires a significant change in perspective for a Java developer.
Someone wise once said "premature optimization is the root of all evil." I believe that applies in this case.
As others have expressed, you don't want to abstract for the sake of flexibility until you have an actual need for the abstraction. Otherwise you end up doing more work than necessary, and introducing unnecessary complexity before it is required. This costs money and actually makes your code more brittle.
Also, if your code is well organized and well tested, you should not be afraid of major changes. Code is always changing, and trying to anticipate and optimize for a change that may or may not come will almost always get you in more trouble than it saves you.
Acknowledgement: I should give credit to Agile programming and my practice and readings on the topic. What I've said comes directly from my understanding of Agile, and I've found it to be an extremely good razor to cut out the extra fat of my work and get lots done. Also none of what I've said is actually JavaScript specific... I'd apply those principles in any language.
There are good arguments calling this development practice - wrapping in order to switch later - into question in any language.
A good quote by Oren Eini, from his writeup on wrapping ORMs:
Trying to encapsulate to make things
easier to work with, great. Trying to
encapsulate so that you can switch
OR/Ms? Won’t work, will be costly and
painful.
This is definitely something that is done in enterprise environments.
Take for example a company that has their own custom javascript framework that is used on all of their projects. Each of the projects decide to use their own framework (jQuery, Dojo, Prototype) to add functionality to the underlying modules of the company framework. Employees that move between projects can now easily do so because their API with working the project's codebase is still the same, even though the underlying implementation could be different for each project. Abstraction is helpful in these situations.
It is overkill. Javascript is not Java and is not in any way related to Java. It is a completely different language that got J-a-v-a in the name for marketing reasons.
If you are concerned with availability of add-on libraries, then choose a framework with a large ecosystem. In an enterprise environment you will be further ahead by standardising on a vanilla off-the-shelf uncustomised web framework that you can upgrade every year or so tracking the rest of the world. And then supplement that with a SMALL in-house add-on library which you will, of course, have to maintain yourself, not to mention training any new programmers that you hire.
Since you are talking about Javascript in the client (web browser) it is more important that you limit the complexity of the things that people do with it. Don't build huge amounts of client side code, and don't make stuff that is so brittle that another programmer can't maintain it. A web framework helps you both keep the linecount down, and keep your own code reasonably simple.
It is not a question of Javascript best practice, because that would be different for server-side JS such as Rhino or node.js.
Adapter pattern is not a common solution in this case. The only example I know to use this pattern is extjs. Javascript projects are usually too small and they aren't worth the effort you would make by creating such an abstraction layer.
The common solution for this problem is that you try to use multiple frameworks together for example with jquery.noConflict.
I've done this before, and can talk a bit about the experience of writing a library/toolkit wrapper.
The plan was to move from Prototype to some other library. Dojo was the first choice, but at the time I wasn't sure whether that's the library to move everything to (and by everything I mean ~5MB of Prototype-happy JS). So coming from a world of clean interfaces, I was set to write one around Prototype and Dojo; an awesome interface that would make switching out from dojo a breeze, if that was in fact necessary.
That was a mistake that cost a lot of time and effort for a few reasons. The first one is that although two libraries can provide the same functionality, (a) their API will almost always be different, and most importantly (b) the way you program with one library will be different.
To demonstrate, let's take something as common as adding a class-name:
// Prototype
$("target").addClassName('highlighted');
// Dojo
dojo.addClass("target", "highlighted");
// jQuery
$("target").addClass("highlighted");
// MooTools
$('target').set('class', 'highlighted');
Pretty straight-forward so far. Let's complicate it a bit:
// Prototype
Element.addClassName('target', 'highlighted selected');
// Dojo
dojo.addClass("target", ["highlighted", "selected"]);
// jQuery
$("target").addClass(function() {
return 'highlighted selected';
});
// MooTools
$("target").set({
"class": "highlighted selected"
});
Now after choosing an interface for your version of the addClass you have two options: (1) code to the lowest common denominator, or (2) implement all of the non-intersecting features of the libraries.
If you go with the 1st -- you'll loose the "personality" / best qualities of each of the library. If you go with #2 -- your addClass' code will be at 4 times larger than the ones provided by any of the libraries, since for example when Dojo is included, you'll have to write the code for the function as the first param (jQuery) and the Object as the first param (MooTools).
Therefore, although it is theoretically possible, it isn't practical, but is a very nice way to understand the intricacies of the libraries out there.
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 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.