eslint-import-file-extension

This Eslint 9+ plugin enforces local ES module imports to have the .js file extension.

Example

Since ES module imports of TypeScript files aren't (and never will be) rewritten to JavaScript imports, we have to enforce imports to have the .js file extension, even when importing TypeScript files. Here is a summary on why TypeScript works the way it does.

This is an example of an invalid import:

import something from './myfile.ts'

After the TypeScript compiler has transpiled this statement, it'll still reference myfile.ts, which will generate errors since myfile.ts will have been transpiled to myfile.js.
Instead, the original code must reference myfile.js as that's the name of the file that will be produced by the TypeScript compiler.

The original source code should look like this:

import something from './myfile.js'

Now, we can be confident that, even after TS transpilation, our code will work.

This ESLint plugin enforces such imports.

Installation

ESLint version >=9.0.0 is required to use this plugin. This plugin is not compatible with ESLint version 8 and lower.

Add the plugin as a development dependency:

npm i --save-dev @larsdroid/eslint-import-file-extension

Enable the plugin from eslint.config.js:

import eslintPluginImportFileExtension from '@larsdroid/eslint-import-file-extension'

export default [
    // other exisiting configuration here ...
    {
        // configuration such as `languageOptions` should be here ...
        plugins: {
            'eslint-import-file-extension': eslintPluginImportFileExtension
        },
        rules: {
            'eslint-import-file-extension/js-file-extension': 'error'
        }
    }
]

Issues

Issues can be reported here.