ts2mjs

Rename TypeScript created ESM .js files to .mjs

This tool takes output from tsc and copies/renames the files.

- file.js => file.mjs
- file.js.map => file.mjs.map
- file.d.ts => file.d.mts
- file.d.ts.map => file.d.mts.map
- file.ts => file.mts (by default, can be skipped with --skip-ts)

CommonJS Support

Use the --cjs flag to generate CommonJS extensions instead:

- file.js => file.cjs
- file.js.map => file.cjs.map
- file.d.ts => file.d.cts
- file.d.ts.map => file.d.cts.map
- file.ts => file.cts (by default, can be skipped with --skip-ts)

Key Features

$3

Automatically updates relative imports and exports in your files:

dist/code.js -> dist/code.mjs

``diff
import * as path from 'path';
import { lib } from 'package/lib/index.js'
-import { findFiles } from './findFiles.js';
+import { findFiles } from './findFiles.mjs';
`

dist/index.d.ts -> dist/index.d.mts

`diff
-export { PrimeNumber, Tuple, GUID, Address, Person, Annotation, } from './types.js';
+export { PrimeNumber, Tuple, GUID, Address, Person, Annotation, } from './types.mjs';
-export { lookUpPerson } from './lookup.js';
+export { lookUpPerson } from './lookup.mjs';
`

$3

Use --remove-source to automatically delete original files after successful conversion:

`sh
ts2mjs dist/esm --remove-source


Original .js files are deleted after being converted to .mjs


`

$3

Use --skip-ts to ignore TypeScript files instead of converting them:

`sh
ts2mjs dist/esm --skip-ts


.ts and .d.ts files are left unchanged, only .js files are processed


`

Options

- --cjs - Generate .cjs extensions instead of .mjs
- --remove-source - Remove original files after successful conversion
- --skip-ts - Skip all TypeScript files (.ts and .d.ts) instead of converting them
- --dry-run - Preview changes without making them
- --verbose - Show detailed output
- -o, --output

- Specify output directory (default: in-place)
- --root - Set the root directory for processing

Usage

This is an example on how to create a package that exports both CommonJS and ESM from TypeScript source.

tsconfig.esm.json

`jsonc
{
"$schema": "https://json.schemastore.org/tsconfig",
"extends": "@tsconfig/node20/tsconfig.json",
"compilerOptions": {
"declaration": true,
"module": "ES2022",
"moduleResolution": "node",
"outDir": "dist/esm",
"sourceMap": true
},
"include": ["src"]
}
`

tsconfig.cjs.json

`jsonc
{
"$schema": "https://json.schemastore.org/tsconfig",
"extends": "@tsconfig/node20/tsconfig.json",
"compilerOptions": {
"declaration": true,
"module": "NodeNext",
"moduleResolution": "NodeNext",
"outDir": "dist/cjs",
"sourceMap": true
},
"include": ["src"]
}
`

package.json

`json
{
"type": "commonjs",
"main": "dist/csj/index.js",
"module": "dist/esm/index.mjs",
"types": "dist/cjs/index.d.ts",
"exports": {
".": {
"import": "./dist/esm/index.mjs",
"require": "./dist/cjs/index.js"
}
}
}
`

$3

`sh


Build both CommonJS and ESM

tsc -p tsconfig.cjs.json
tsc -p tsconfig.esm.json

Convert ESM output to .mjs

ts2mjs dist/esm

Convert CJS TypeScript files to .cts (if needed)

ts2mjs dist/cjs --cjs

Advanced usage examples

ts2mjs dist/esm --remove-source # Delete original files after conversion
ts2mjs dist/esm --skip-ts # Only process .js files, skip .ts/.d.ts
ts2mjs dist/esm --dry-run --verbose # Preview changes with detailed output
`

Help

`
Usage: ts2mjs [options]

Rename ESM .js files to .mjs (or .cjs if --cjs options is used)

Arguments:
files Globs matching files to rename.

Options:
--cjs Use .cjs extension instead of .mjs extension.
-o, --output

The output directory.
--cwd The current working directory.
--root The root directory.
-x,--exclude Exclude a glob from the files. (default: [])
--dry-run Dry Run do not update files.
--remove-source Remove the original files after successful conversion.
--skip-ts Skip all TypeScript files (.ts and .d.ts) instead of
converting them.
--no-must-find-files No error if files are not found.
--no-enforce-root Do not fail if relative .js files outside of the root
are imported.
--color Force color.
--no-color Do not use color.
-v, --verbose Verbose mode
-V, --version output the version number
-h, --help display help for command
``

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