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MJS TS
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Convert MJS to TS

Verified by Adam B.· reviewed by FE Editorial ·updated Aug 12, 2026
QUICK ANSWER
Is it possible to convert MJS to TS?
Yes - MJS converts to TS.

Rename file.mjs to file.ts and it is already valid TypeScript, since existing JavaScript is legal TS. You then add type annotations where the compiler flags errors, and tsc compiles it back to JavaScript for running.

Also to TS: REC · JS · TRP

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Tested on macOS, Windows & Linux
Last verified Sep 2026

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Why convert MJS to TS?

Developers convert .mjs to .ts to gain static type checking and editor autocompletion while keeping the same ES-module structure they already wrote.

How to convert MJS to TS

Rename to .ts / .mts EASIEST

Rename the file to .ts (or .mts to force ESM output); the import/export statements work as-is and you add types incrementally.

TypeScript compiler (tsc) OPEN-SOURCE

Set "allowJs": true in tsconfig.json, then run tsc to type-check and emit JavaScript; tighten strict once errors are resolved.

Visual Studio Code FREE

Open the renamed .ts in VS Code; its built-in TypeScript service surfaces missing types and quick-fixes to add annotations.

esbuild OPEN-SOURCE

Run esbuild file.ts --outfile=file.js to strip the types fast for a build, though esbuild does not type-check.

About these formats

.MJS Node.js ES Module File

An .mjs file is JavaScript source code that Node.js treats as an ECMAScript module, meaning it uses import and export instead of CommonJS require. The extension exists so Node can tell ES…

Open .MJS details →
.TS MPEG Transport Stream

A .ts file is an MPEG Transport Stream - a video container format from digital TV, PVR recordings, AVCHD camcorders, and HLS streaming. VLC media player opens it on any OS. To convert it to…

Open .TS details →

Quality & what to watch

  • Renaming makes the file valid TS, but it gains no real safety until you add annotations and enable strict checks.
  • tsc reports type errors that plain JavaScript ignored, so you may need to fix implicit any and untyped imports.
  • esbuild transpiles without type-checking, so use tsc --noEmit alongside it to actually catch type errors.

Frequently asked questions

Is `.mjs` valid TypeScript?
Yes. TypeScript is a superset of JavaScript, so a renamed .mjs compiles as .ts even before you add any type annotations.
Should I use `.ts` or `.mts`?
Use .mts when you want the output to stay an ES module regardless of package.json. Use .ts and let tsconfig.json and the package type decide.
Do my imports still work?
Yes, ESM import/export syntax carries over unchanged into TypeScript. You only add type information on top of it.
How do I run the resulting TypeScript?
Compile it with tsc to JavaScript and run that, or use a runner like tsx or ts-node that transpiles on the fly.