Meteor is a set of new technologies for building top-quality web apps in a fraction of the time, whether you're an expert developer or just getting started.

I am soo going to play around with this next weekend! This looks truly promising and fun :)

Grunt is a task-based command line build tool for JavaScript projects.

Grunt is a task-based command line build tool for JavaScript projects.

jQuery has matured as the de facto standard js library. However time has passed and interesting new frameworks like Zepto.js have appeared. Can they challenge jQuery's predominance?

Pngy is a bit of jQuery that allows you to load images of different file sizes based on a page’s load speed. So, if the load speed is slow, Pngy can load your small image. If it’s fast, it can load a hi-res image. It’s kinda like a ping test in Javascript.

Resonates with my ideas on responsive images

Pngy (GitHub) →

Before we have a real solution like the proposed element, plugins like pngy will make life a little better for us

I'm a Christian and a Family Man. I develop at appendTo providing jQuery and JavaScript Consulting. I'm an ASP.NET MVP and a ASPInsider. I'm also active on Twitter and Google+.
--> { "name": "Elijah Manor", "priorities" : [ "Christian", "Family", "Work" ], "employer" : "appendTo", "title" : [ "Senior Architect", "Trainer" ], "tech" : [ "JavaScript", "jQuery", "HTML5" ], "awards" : [ "Microsoft Regional Director", "ASP.NET MVP", "ASPInsider" ], "social": [ "Twitter", "Google+", "LinkedIn" ] }

Interesting findings abouts the differences between jQuery bind, live, delegate and on

A nice overview / comparison between two popular frameworks for writing complex javascript applications.

The Play framework makes it easier to build Web applications with Java and Scala

Finally a Java Web framework made by Web developers. Discover a clean alternative to bloated enterprise Java stacks. Play focuses on developer productivity and targets RESTful architectures.

I discovered the play framework today and after going through a bit of the blog tutorial I must say that I like it a lot!

See what kind of things can be done with JavaScript

I was recently reminded about Dmitry Baranovsky’s Javascript test, when N. Zakas answered and explained it in a blog post. First time I saw those questions explained was by Richard Cornford in comp.lang.javascript, although not as thoroughly as by Nicholas.

I decided to come up with my own little quiz. I wanted to keep question not very obscure, practical, yet challenging. They would also cover wider range of topics.

Host objects

Contrary to Dmitry’s test, quiz does not involve host objects (e.g. window), as their behavior is unspecified and can vary sporadically across implementations. We are talking about pure ECMAScript (3rd ed.) behavior. Now, it’s worth pointing out that sometimes implementations deviate from the standard collectively, forming their own, de-facto standard. An example of this is for-in statement, where none of the popular implementations throw TypeError when expression evalutes to null or undefined — for (var prop in null) { ... } — and instead just silently ignore it. I tried to avoid these non-standard cases. Every question has a correct answer that can be reproduced in at least one of the major implementations.

So what are we testing?

Not a lot really. Quiz mainly focuses on knowledge of scoping, function expressions (and how they differ from function declarations), references, process of variable and function declaration, order of evaluation, and a couple more things like delete operator and object instantiation. These are all relatively simple concepts, which I think every professional Javascript developer should know. Most of these are applied in practice quite often. Ideally, even if you can’t answer a question, you should be able to infer answer from specs (without executing the snippet). When creating these questions, I made sure I can answer each one of them off the top of my head, to keep things relatively simple.

Note, however, that not all questions are very practical, so don’t worry if you can’t answer some of them. We don’t often use with statement, for example, so failing to know/remember its exact behavior is understandable.

Few notes about code

• Assuming ECMAScript 3rd edition (not 5th)
• Implementation quirks do not count (assuming standard behavior only)
• Every snippet is run as a global code (not as eval or function one)
• There are no other variables declared (and host environment is not extended with anything beyond what’s defined in specs)
• Answer should correspond to exact return value of entire expression/statement (or last line)
• “Error” in answer indicates that overall snippet results in a runtime error

Quiz

Please make sure you select answer in each question, as lack of answer is not checked and counts as failure. The final score is simply a number of wrong answers, less is better. Quiz requires Javascript to be enabled.

1. (function(){ 
         return typeof arguments;
       })();

   • “object”
   • “array”
   • “arguments”
   • “undefined”

2. var f = function g(){ return 23; };
       typeof g();

   • “number”
   • “undefined”
   • “function”
   • Error

3. (function(x){
         delete x;
         return x;
       })(1);

   • 1
   • null
   • undefined
   • Error

4. var y = 1, x = y = typeof x;
       x;

   • 1
   • “number”
   • undefined
   • “undefined”

5. (function f(f){ 
         return typeof f(); 
       })(function(){ return 1; });

   • “number”
   • “undefined”
   • “function”
   • Error

6. var foo = { 
         bar: function() { return this.baz; }, 
         baz: 1
       };
       (function(){ 
         return typeof arguments[0]();
       })(foo.bar);

   • “undefined”
   • “object”
   • “number”
   • “function”

7. var foo = {
         bar: function(){ return this.baz; },
         baz: 1
       }
       typeof (f = foo.bar)();

   • “undefined”
   • “object”
   • “number”
   • “function”

8. var f = (function f(){ return "1"; }, function g(){ return 2; })();
       typeof f;

   • “string”
   • “number”
   • “function”
   • “undefined”

9. var x = 1;
       if (function f(){}) {
         x += typeof f;
       }
       x;

   • 1
   • “1function”
   • “1undefined”
   • NaN

10. var x = [typeof x, typeof y][1];
        typeof typeof x;

    • “number”
    • “string”
    • “undefined”
    • “object”

11. (function(foo){
          return typeof foo.bar;
        })({ foo: { bar: 1 } });

    • “undefined”
    • “object”
    • “number”
    • Error

12. (function f(){
          function f(){ return 1; }
          return f();
          function f(){ return 2; }
        })();

    • 1
    • 2
    • Error (e.g. “Too much recursion”)
    • undefined

13. function f(){ return f; }
        new f() instanceof f;

    • true
    • false

14. with (function(x, undefined){}) length;

    • 1
    • 2
    • undefined
    • Error

You've got 0 answers wrong.
Flawless victory.

Let’s see the score!

I hope you liked it. Please leave your score in the comments. I’ll try to explain these questions sometime in a near future, unless someone else does it before me. Meanwhile, you can take a look at my articles on function expressions and delete operator, understanding which would help you answer some of these questions, and more importantly, explain their answers.

Think you kow JavaScript? Then try this ;)