 <p><code>--ext</code> allows using custom javascript extensions, you can't force ESLint to work for languages other than JavaScript by passing a different file extension to it.</p> <p>You can try using <a href="https://github.com/eslint/typescript-eslint-parser" rel="nofollow">typescript-eslint-parser</a> to enable ESLint for Typescript - it allows building a syntax tree from typescript code that can be passed to ESLint for linting.</p> <p>But I'd suggest using Typescript linters for inspecting TypeScript code. You can try <a href="https://github.com/palantir/tslint" rel="nofollow">TSLint</a>, for example.</p>