`if __name__ == '__main__'` equivalent in javascript es6 modules

Question

Is it possible to check if JavaScript file is being run directly or if it was required as part of an es6 module import.

for example a main script is included.

<

Answer 1

module.parent will help you:

if(module.parent) {
    console.log('required module')
} else {
    console.log('main')
}

Answer 2

The solution I see there is just to define the variable in the script you're importing. I.e. you define mainTest in main.js, and then use your existing if block.

Answer 3

An alternative for ES6 modules is now supported in Node. Using the new import.meta builtin.

Example:

// main.mjs
import { fileURLToPath } from "url";
import "./lib.mjs"

if (process.argv[1] === fileURLToPath(import.meta.url)) {
  console.log(`main ran!`);
}

// lib.mjs
import { fileURLToPath } from "url";

if (process.argv[1] === fileURLToPath(import.meta.url)) {
  console.log(`lib ran!`);
}

and our output:

main ran!