README.md

Creating standalone ESM-based Node.js scripts on Unix and Windows

Approach:

1. The file starts with shell code.
2. That code uses Node.js to execute the file in ESM mode, after it removes the initial non-JavaScript lines.
   • Node.js does not currently have CLI flags for achieving what we do in this step. Therefore, we have to pipe to the node executable.

When editing this file, we want to use the JavaScript mode of our IDE or editor. Therefore, we try to “hide” the shell code from JavaScript as much as possible.

Suggestions for improvements welcome!

myscript

#!/bin/sh
':' // ; tail --lines=+3 "$0" | node --input-type=module - $@ ; exit $?

// --lines=+3 removes 2 lines

import * as os from 'node:os';
console.log(os.homedir());
console.log(process.argv);


// Standalone ESM-based Node.js script on Unix
// Explanations: https://sambal.org/2014/02/passing-options-node-shebang-line/

myscript.bat

:: /*
@echo off
more +5 %~f0 | node --input-type=module - %*
exit /b %errorlevel%
*/

import * as os from 'node:os';
console.log('HOME', os.homedir());
console.log(process.argv);


// Standalone ESM-based Node.js script on Unix

Very nice! A couple of tiny mods to myscript.bat you might consider? Changing %0 to %~f0 in line 3 would allow invoking from the Windows command line using simply myscript rather than myscript.bat. Also changing 0 in line 4 to %errorlevel% would propagate any exit code to a parent process:

more +5 "%~f0" | node --input-type=module
exit /b %errorlevel%

@sgourley Excellent suggestions, thanks! I’ve changed myscript.bat accordingly.