'Error: 'types' can only be used in a .ts file - Visual Studio Code using @ts-check

I am starting to use TypeScript in a Node project I am working on in Visual Studio Code. I wanted to follow the "opt-in" strategy, similar to Flow. Therefore I put // @ts-check at the top of my .js file in hope to enable TS for that file. Ultimately I want the same experience of "linting" as Flow, therefore I installed the plugin TSLint so I could see Intellisense warnings/errors.

But with my file looking like:

// @ts-check

module.exports = {
  someMethod: (param: string): string => {
    return param;
  },
};

and my tsconfig.json file looking like...

{
  "compilerOptions": {
      "target": "es2016",
      "module": "commonjs",
      "allowJs": true
  }
}

I get this error: [js] 'types' can only be used in a .ts file. as shown below in the image.

I saw this question which recommended disabling javascript validation in vscode but then that doesn't show me any TypeScript Intellisense info.

I tried setting tslint.jsEnable to true in my vscode settings as mentioned in the TSLint extension docs but no luck there.

What is the correct setup in order to use .js files with TypeScript and get Intellisense so I know what the errors in my code are before I run any TS commands?

Solution 1:^[1]

Use "javascript.validate.enable": false in your VS Code settings, It doesn't disable ESLINT. I use both ESLINT & Flow. Simply follow the instructions Flow For Vs Code Setup

Adding this line in settings.json. Helps "javascript.validate.enable": false

Solution 2:^[2]

I followed following steps to fix the issue:

Go to Preferences and then to settings:

After going to settings search for javascript.validate in the search bar and uncheck the checkbox:

if you want to edit it via json then: Go to: Code -> Preferences -> Settings -> Extensions -> Scroll down and find "Edit in settings.json". then add

"javascript.validate.enable": false

Solution 3:^[3]

For anyone who lands here and all the other solutions did not work give this a try. I am using typescript + react and my problem was that I was associating the files in vscode as javascriptreact not typescriptreact so check your settings for the following entries.

   "files.associations": {
    "*.tsx": "typescriptreact",
    "*.ts": "typescriptreact"
  },

Solution 4:^[4]

You must use a .ts file - e.g. test.ts to get Typescript ~~validation, intellisense~~ typing of vars, return types, as well as "typed" error checking (e.g. passing a string to a method that expects an number param will error out).

It will be transpiled into (standard) .js via tsc.

Update (11/2018):

Clarification needed based on down-votes, very helpful comments and other answers.

types

Yes, you can do type checking in VS Code in .js files with @ts-check - as shown in the animation
What I originally was referring to for Typescript types is something like this in .ts which isn't quite the same thing:

hello-world.ts
```
function hello(str: string): string {
  return 1;
}

function foo(str:string):void{
   console.log(str);
}
```
This will not compile. Error: Type "1" is not assignable to String
if you tried this syntax in a Javascript hello-world.js file:
```
//@ts-check

function hello(str: string): string {
  return 1;
}

function foo(str:string):void{
   console.log(str);
}
```
The error message referenced by OP is shown: [js] 'types' can only be used in a .ts file

If there's something I missed that covers this as well as the OP's context, please add. Let's all learn.

Solution 5:^[5]

"typescript.validate.enable": false

IN VS Code -> Preferences -> Settings -> Search for above mentioned property and disable the property

Solution 6:^[6]

The solution that worked for me was adding the following property to settings.json:

"js/ts.implicitProjectConfig.checkJs": true

Solution 7:^[7]

Just default the variable to the expected type:

(number=1) => ...
(number=1.0) => ...
(string='str') ...

Solution 8:^[8]

For VS code in windows, click on settings. Then on the search bar at the top, type javascript validate and just uncheck the checkbox as shown below.

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution	Source
Solution 1	chengsam
Solution 2
Solution 3	Andy
Solution 4
Solution 5	Srini Karthikeyan
Solution 6	Jonatan Ramírez Medina
Solution 7	dippas
Solution 8	kayleb

'Error: 'types' can only be used in a .ts file - Visual Studio Code using @ts-check

Solution 1:[1]

Solution 2:[2]

Solution 3:[3]

Solution 4:[4]

Update (11/2018):

Solution 5:[5]

Solution 6:[6]

Solution 7:[7]

Solution 8:[8]