Question : Is typescript compiler can compile javascript files instead typescript files?

[ifle]

Will be nice if typescript compiler can compile javascript code instead typescript.
We would like to start to use the async\await syntax only with ES5 target and use as input the js files.

[aluanhaddad]

It can. Have you tried --allowJs?

You will want to set --outDir otherwise it will fail with Error: would overwrite input file.

[ifle]

I tried allowJs flag, but it does not work in Visual Studio

[mhegazy]

I tried allowJs flag, but it does not work in Visual Studio

what do you mean by does not work? how are you calling the compiler?

[ifle]

I rechecked again. The allowJs flag does not works in saving a file in VS2015 Update3
I have following tsconfig

{
  "compileOnSave": true,
  "compilerOptions": {
    "noImplicitAny": false,
    "noEmitOnError": false,
    "removeComments": false,
    "sourceMap": true,
    "listEmittedFiles": true,
    "target": "es5",
	  "lib": [
              "dom",
              "es5",            
              "es2015.promise"
          ],
      "outDir": "./html/js",
      "allowJs": true
  },
  "include": [
        "./html/ts/*"
    ],
  "exclude": [
    "node_modules",
    "wwwroot"
  ]
}

[mhegazy]

Compile-on-save will not work for .js files in VS 2015; this should be supported in VS 2017 now.

Build should generate the files in both versions.

[ifle]

You are right. Build work, compile on save does not work. Is there any plans to fix this issue?

[mhegazy]

The fix requires some major rearchitecture of both the JS and TS language services in VS; something that we already have done in VS 2017, and have no plans to back-port to VS 2015 at the time being.

[ifle]

Thanks for your answer.

[styfle]

@mhegazy Is this enabled by default in VS 2017? I noticed a bunch of javascript files generated a corresponding .map.js and their formatting was changed a bit after compiling and existing VS 2015 project.

[mhegazy]

if your project has both --allowJs: true and compileOnSave enabled, then yes. the output should be the same though, if it is different then there is a miss configuration/compiler bug somewhere. If you can share more details we can investigate more.

[styfle]

I am not using the tsconfig.json or setting any command line flags myself. The property group looks like the following:

<PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Build|AnyCPU'">
    <DebugSymbols>true</DebugSymbols>
    <OutputPath>bin\</OutputPath>
    <DefineConstants>TRACE</DefineConstants>
    <DebugType>full</DebugType>
    <PlatformTarget>AnyCPU</PlatformTarget>
    <ErrorReport>prompt</ErrorReport>
    <CodeAnalysisRuleSet>MinimumRecommendedRules.ruleset</CodeAnalysisRuleSet>
    <TypeScriptTarget>ES5</TypeScriptTarget>
    <TypeScriptJSXEmit>React</TypeScriptJSXEmit>
    <TypeScriptCompileOnSaveEnabled>True</TypeScriptCompileOnSaveEnabled>
    <TypeScriptNoImplicitAny>True</TypeScriptNoImplicitAny>
    <TypeScriptModuleKind>CommonJS</TypeScriptModuleKind>
    <TypeScriptRemoveComments>False</TypeScriptRemoveComments>
    <TypeScriptOutFile />
    <TypeScriptOutDir />
    <TypeScriptGeneratesDeclarations>False</TypeScriptGeneratesDeclarations>
    <TypeScriptNoEmitOnError>True</TypeScriptNoEmitOnError>
    <TypeScriptSourceMap>True</TypeScriptSourceMap>
    <TypeScriptMapRoot />
    <TypeScriptSourceRoot />
  </PropertyGroup>

I believe it might be related to #14565 but the other reason might be if the default is now true in VS 2017 when it was false in VS 2015 (TS 1.8).

[mhegazy]

@styfle can you elaborate on the details of the issues you are seeing? you have .js files in your project, when you save them, you see output generated for them in your bin\ dir, and no tsconfig.json? is this accurate?

[billti]

<TypeScriptOutDir /> is empty above, so its likely not compiling as the output would overwrite the input. Can you specify a location to put the compiled files and see if that works?

[styfle]

I am not using a bin folder. The .js file gets generated next to the .ts file.

Steps to reproduce

I opened an existing 2015 project in VS 2017, edited a .d.ts file, saved, and VS started compiling a lot of files....files that do not have a .ts associated with them 😨

Then I looked at git changes in Team Explorer tab and I can see that a bunch of .js files were modified and a bunch of .js.map files were added.