Is Jquery *compiler* possible?

I think what you mean is: if you write

var myId = $("#myId")

it will be converted to

var myId = document.getElementById("myId")

I think its possible, but the problem is, jQuery functions return jQuery objects, so in the above example, the first myId will be a jQuery object & the second will be a node object(i think) which will affect other functions that needs to use it later in the code after compilation. Especially if they are chained

secondly you will have to be sure that the conversion actually has performance benefits.However if you are aware of all this and you can plan you code accordingly, i think it will be possible

If the purpose of the compiler to convert Javascript (which may be jquery or anything) to better Javascript (which I understood from you saying "ultimately executed"), then Google has already done that. They made closure compiler and some have tried it with JQuery in this post. Isn't this what you are suggesting ?

jQuery code is "raw JavaScript code" so I'm not sure what a compiler would really buy you. That's like writing a C# compiler which takes C# 4.0 code and emits C# 1.1 code. What's the benefit?

jQuery isn't a different language which replaces or even sits on top of JavaScript. It's a framework of JavaScript code which provides lots of useful helpers for common tasks. In my view, it's greatest benefit is that its distinctive structure helps to differentiate it from the more "Java-like" languages.

JavaScript by itself is deceptively similar to other languages and this tends to be one of its biggest faults as a language. People try to think of it in terms of Java, even though the similarities pretty much stop at the name. Structurally, JavaScript is very different in many ways (typing, scope, concurrence, inheritance, polymorphism, etc.) and I particularly like how jQuery and other modern JavaScript projects have brought the language to stand on its own merits.

I guess to get back to the question... If you're looking to turn jQuery-style JavaScript into Java-style JavaScript, then that's something of a step backwards. Both versions would be interpreted by the browser the same way, but one of the versions is less elegant and represents the language more poorly than the other.

Note that jQuery isn't the only framework that does these things, it's just the most popular. Would such a compiler need to also handle all the other frameworks? They all do different things in different ways to take advantage of the language. I don't think that homogenizing them to a "simpler" form buys us anything.

Edit: (In response to the various comments around this question and its answers, kind of...

How would you structure this compiler? Given that (as we've tried to point out) jQuery is JavaScript and is just a library of JavaScript code, and given how browsers and JavaScript work, your "compiler" would just have to be another JavaScript library. So essentially, what you want is to go from:

• A web page
• The jQuery library
• Some JavaScript code which uses the jQuery library

to:

• A web page
• The jQuery library
• Some JavaScript code which uses the jQuery library
• Your "compiler" library
• Some more JavaScript code which sends the previous JavaScript code through your library somehow
• Your "jQuery-equivalent" library
• Some more JavaScript code which replaces the original JavaScript code with your new version

in order to make things simpler? Or to somehow make debugging tools like FireBug easier to use? What you're proposing is called an "obfuscator" and its sole purpose is to make code more difficult to reverse-engineer. A side effect is that it also make code more difficult to understand and maintain.