javascript - Is Jquery *compiler* possible?

Question

When I saw this question I thought it would be helpful if a jQuery compiler could be written. Now, by compiler, I mean something that takes in jQuery code and outputs raw javascript code that is ultimately executed.

This is how I vision a block of jQuery code execution:

1. a jQuery function is called and parameters are passed to it
2. the function calls a raw javascript function and passes the parameters it received to it
3. the newly called function performs the intended action

I understand that this is a very simplified model and it could be much more complex, but I think the complexity is reduced to steps 2 and 3 being repeated with different raw js functions being called and each time fed with all or a subset of parameters / previous results.

If we subscribe to that model, then we might come up with methods to make the jQuery functions perform double-duty:

1. What they already do
2. Logging what they did in form of raw_function(passed_params)

Am I making some wrong assumptions that would make this impossible? Any ideas how Firebug's profiler attempts to get function names? Could it be used here?

Edit

What I was thinking was making a black box with input / output as:

normal jquery code → [BB] → code you'd write if you used no library

• I called this a compiler, because you compiled once and then would use the resulting code.
• I argued that it could have at least educational use, and probably other uses as well.
• People said this would take in a small amount of code and output a huge mass; that does not defy the intended purpose as far as I see
• People said I'd be adding an extra, needless step to page rendering, which, given only the resulting code would ultimately be used (and probably be used just for studying), is not correct.
• People said there is no one-to-one relation between javascript functions and jquery functions, and implied such a converter would be too complicated and probably not worth the effort. With this I now agree.

Thank you all!

Answer 1

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