Identify JavaScript function parameters

[RexSkz]

Support parameters for these types of functions:

// es6 class method
foo(x, y) {}
// es6 arrow function
(x, y) => x
x => x
// es5 function
function foo(x, y) {}
// es5 anonymous function
function (x, y) {}

[RunDevelopment]

Shouldn't this be async\s+ ?

[RexSkz]

If we use async\s+, we couldn't match the variable foo in foo = async(a, b) =>, where the async here is a reserve word instead of the function name.

I found a better solution async(?:(?:\s*(?=\())|\s+).

[RunDevelopment]

This will also match functionAbc(). Maybe something like this is more suitable:

/(function)(?:\s+[_$a-z\xA0-\uFFFF][$\w\xA0-\uFFFF]*)?\s*(\([^()]*\))/

[RexSkz]

You are right, I'll fix my code. Thanks~

[RunDevelopment]

First of all, I like this RP.
We could use this to fix the false positives of keywords in parameter names (like in the API docs). You don't currently do that, but we could.

Now for the execution:

1. I don't get why you don't just put everything you don't want (function name) in lookarounds?
2. We don't you just make one 'parameter': [ /* patterns */ ]? This will save you from using this many aliases.

Apart from that, I like it.
(Even though this might not equate to much because I'm not a maintainer or anything...)

[RexSkz]

@RunDevelopment

1. Do you mean those reserve words in the regex for es6-class-method-parameter? I thought in a normal JS code, beside function names, only those words will appear before a (. If someone thinks it hard to find all possible words, I will put all JS reserve words in it.
2. I didn't realize I can use an array here, will fix my code soon.

[RunDevelopment]

@RexSkz

Because we need to identify function name too, function name is also wrapped in parameters. This is not the best idea, but I can't find another way.

I meant that despite the name parameter, you not only match the parameters, but also the function name itself. This is somewhat confusing, so I wanted to suggest, that the function name (and trailing spaces) should be included into a lookbehind.
I don't know if this approach given us trouble identifying the function name itself, so maybe I'm overlooking something?

[RexSkz]

@RunDevelopment

I just found another way to exclude "function name" from "parameters": exclude () from "parameters" at the same time so Prism can keep using ( to recognize "function".

A new commit was just created.

[RunDevelopment]

2 Problems here:

1. You probably don't want trailing spaces, so please make it [^()]*?. Otherwise (?=\s* won't match anything.
2. This also matches function a()). Not valid JS, I know, but still. Replace \S with [^\s()] and your good to go.

[RunDevelopment]

Leading and trailing spaces might not be wanted.

[RunDevelopment]

1. There might be problems with \S again.
2. Spaces?
3. awaitSomething(a){} is not matched. Neither is $await(a){} (\b might not have been the best choice).

[RexSkz]

@RunDevelopment

All fixed. Is there any other problems?

[RunDevelopment]

@RexSkz

Not problems, just the suggestion to replace (?:async(?:(?:\s*(?=\())|\s+))?(function with (?:async\s*)?(?:\bfunction. It's less verbose and easier to understand imo.

At last, a question:
One of your expressions uses a bunch of keywords to avoid matching stuff like if(abc){}. Why did you use this specific subset of JS keywords?

/((?:\b|\s|^)(?!(?:await|delete|export|for|if|new|return|switch|throw|typeof|while|yield)(?![$\w\xA0-\uFFFF]))(?:[_$a-z\xA0-\uFFFF][$\w\xA0-\uFFFF]*\s*)\(\s*)[^\s()][^()]*?(?=\s*\)\s*\{)/

[RexSkz]

@RunDevelopment

1. Your suggestion seems good, I'll replace my regex.
2. In normal JS code, beside function names, only those words will appear before a (. Maybe putting all JS keywords here is a better idea? But it will make this regex much longer.

[mAAdhaTTah]

@RunDevelopment Besides the conflict, is this PR ready to go?

[RunDevelopment]

@mAAdhaTTah Yep, I think this is ready to go.

---

Maybe it's time for JS-Extras? (Especially when considering #1468.)

[mAAdhaTTah]

@RunDevelopment I'm OK with this PR in the main JS language; maybe that PR is extensive enough to break it out into a separate language?

[RunDevelopment]

maybe that PR is extensive enough to break it out into a separate language?

@mAAdhaTTah Do you mean the Regex one? If so, then I agree but I think we need to discuss how that language should look like because the JS regex syntax is a very stripped down version of the syntax other languages (e.g. Java, .Net) use. (And they are not necessarly compatible with each other...)

[atomiks]

This doesn't appear to work with destructuring:

function Example({ prop }) {}

[RexSkz]

@atomantic Yes, it's my fault. :-/

Prism now does work with destructuring, but I forgot to add i flag to regex, so it fails when your function name (which I use [_$a-z\xA0-\uFFFF][$\w\xA0-\uFFFF]* to recognize) starts with an uppercase letter. Will make a new PR to fix it.

Update: will be fixed in #1722