A js → ts code migrator,

In the world of misunderstanding, To be As accurate as possible

converts javascript files to typescript — handles module system conversion (commonjs → esm), infers types from ast analysis, extracts jsdoc annotations, refines types with the typescript compiler, and optionally runs eslint --fix.

js → ts migrator by Laxenta INC.

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Install

you can use it directly via pnpm dlx or npx without installing:

pnpm dlx mts-migrator
# or
npx mts-migrator

OR install globally (recommended for frequent cli usage):

pnpm add -g mts-migrator
# or
npm i -g mts-migrator

----------------------------------- Cli usage, All commands are listed --------------------------------

when you run mts (or pnpm mts / npx mts-migrator) without a target, it will prompt you if you want to run it on all folders in your current directory. if you specify a folder name, it will recursively search for a folder with that name so you don't have to specify the exact path!

> IF YOU WANT TO USE TO MIGRATE YOUR FOLDER, JUST COPY THIS COMMAND:

# run interactively (will prompt for confirmation)
pnpm mts

# Or Migrate (to typescript) a specific folder by name (recursively searches for "components named folder")
pnpm mts components

# HELP COMMAND!
pnpm mts --help

# use --target explicitly
pnpm mts --target utils

# preview changes without writing
pnpm mts src --dry-run

# skip ts-morph type refinement
pnpm mts src --no-refine

# skip `eslint --fix` post-processing  
pnpm mts src --no-lint

```bash
# show help
pnpm mts --help

what it does

.js file → parse (babel) → convert modules → inject types → generate .ts
         → refine types (ts-morph) → eslint --fix → done

module conversion

• const fs = require('fs') → import fs from 'fs'
• const { x } = require('y') → import { x } from 'y'
• require('dotenv').config() → import 'dotenv/config'
• module.exports = { x, y } → export { x, y }
• exports.x = y → export { y as x }
• strips .js/.jsx from relative imports
• deduplicates imports from the same source

type inference

• literals: "hello" → string, 42 → number, true → boolean
• constructors: new Map() → Map<any, any>, new Date() → Date
• known apis: Math.floor() → number, process.env.X → string | undefined
• arrays: [1, 2, 3] → number[]
• binary ops: a + b → number or any, a === b → boolean
• jsdoc: @param {string} name → name: string

type refinement (ts-morph)

after the initial babel pass, ts-morph uses the typescript compiler to replace any annotations with actually-inferred types where possible.

eslint integration

if eslint is installed in your project, mts will run eslint --fix on the migrated files automatically. if not, it skips silently.

programmatic api

import { migrateCode, codeToAST, injectTypes, convertModuleSystem } from 'mts-migrator';

// quick: convert a code string
const { code, errors } = migrateCode('const x = require("fs");');

// granular: use individual steps
const { ast } = codeToAST(jsCode);
convertModuleSystem(ast);
injectTypes(ast);
const tsCode = astToCode(ast);

features

• backups: original files are backed up before migration
• dry run: preview what would change without writing
• error recovery: non-fatal parse errors don't block migration
• migration report: json report with per-file status
• config skip: automatically skips config files (webpack, babel, eslint, etc.)

what it doesn't do

• fix logic bugs in your code
• handle flow types (use flow-to-ts for that)
• replace manually-written type annotations
• guarantee zero any in output (but it tries hard)

license

AGPL-3.0

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made with <3 by laxenta inc