Enable the .js and .es file extensions for TypeScript files

[marinasundstrom]

Enable the .js, .jsx, .es and .es6 file extensions for TS compiler file inputs and module imports. This is already supported by other transpilers, such as babel.

The feature would ideally be added as an option in the compiler. With .js together with .ts on by default, but .ts still being prefered.

This would cause the files with the enabled extensions to, just as .ts-files today, be processed (e.g. in and IDE), and transformed if the options so allow it.

One objection to this would be that this could potentially confuse scripts that are using TypeScript-specific features with scripts using official ES6 features. I don't personaly see this as an issue. It is up to the developers to come up with conventions in their own projects.

[dpen2000]

This would probably mean GitHub wouldn't be able to detect whether a repository is using javascript or typescript

[NoelAbrahams]

This would cause the files with the enabled extensions to, just as .ts-files today, be processed (e.g. in and IDE), and transformed if the options so allow it.

What sort of processing are you suggestion for .js files?

[marinasundstrom]

@NoelAbrahams Treating them as TypeScript-files and selectively enabling certain features.

[CyrusNajmabadi]

@RobertSundstrom If you would like them to be treated as TypeScript files, why not rename them to .ts?

[NoelAbrahams]

I actually ran into a use-case today for wanting to compile a .js file.

We have moment.js in a Visual Studio TypeScript project. This is the only JavaScript file in the project. The project has the options "combine output into a single file" and "no implcity any" set.

We want to include moment.js in the combined output file.

I tried setting Build Action: TypeScriptCompile on the properties page for moment.js, but got the error:

moment.js' must have extension '.ts' or '.d.ts'

For the use-case above we cannot simply change the extension to .ts because moment.js is not annotated and will not compile under the noimplicitany flag.

[mhegazy]

@NoelAbrahams this is slightly different from the original proposal from @RobertSundstrom , you want the compiler to read in .js files, write them to the output, but do not report any errors in them. is this accurate?

[NoelAbrahams]

@mhegazy, I would see it as an enhancement to the original request. The following would happen:

• moment.js would be parsed by the compiler and the compiler would report any syntax errors.
• noimplicitany would be ignored, since .js files won't have any type annotation in any case.
• The .js would be included in the output, hence all output options should be honoured, e.g. redirect-output-to-directory, combine-output-into-single-file.

[mhegazy]

What about other semantic errors, e.g.:

var x = 2;
if (false) {
     x = "string":
}

or

var x = 1;

var x = "";

should these be reported for moment.js?

[NoelAbrahams]

I think for most users the processing of .js files is going to be for dealing with very unusual requirements.

We need to include moment.js in a project because non of the major CDN providers that we use (Google/Microsoft) currently host this library.

If people want the compiler to catch semantic errors then they should be writing TypeScript. I think for .js files only syntax errors should be reported.

[Raynos]

👍

I would also like to typecheck javascript files.

My use case is to use the typescript type checker but still author ES5 code that does not need to be compiled for someone to use it.

[ianfp]

+1 Being able to compile files with a .js extension using tsc would be very useful for people like me, who are exploring the possibility of migrating an existing Javascript project to TypeScript. I don't want to have to rename all of my .js files, and I certainly don't want to hack Typescript like this guy suggests.

[kitsonk]

@ianfp it sounds like a totally different problem/subject in that you are looking for a JavaScript -> TypeScript migrator that helps you easily get on the right path of converting a code base from JavaScript to TypeScript. Sounds like an interesting project...

[ianfp]

@kitsonk Perhaps I misunderstood what this issue is about... but yes, I'd basically like to replace r.js with tsc as my compiler and then start migrating the code from there. Perhaps this is not possible?

[forbesmyester]

I'd like to run TS as an extra to ESLint (sometimes) but also be able to benefit from some of the advanced type stuff you guys have available autocompletion in VIM.