es-main

What is es-main?

The es-main npm package is a utility that helps determine if a module is being run directly or being imported as a module. This can be particularly useful for writing scripts that can be both executed directly and imported as part of a larger application.

What are es-main's main functionalities?

Check if a module is the main module

This feature allows you to check if the current module is being run directly or being imported. The code sample demonstrates how to use the es-main package to print a message based on the module's execution context.

const esMain = require('es-main');

if (esMain(import.meta)) {
  console.log('This module is being run directly.');
} else {
  console.log('This module is being imported.');
}

Other packages similar to es-main

is-main

The is-main package provides similar functionality by checking if the current module is the main module. It is simpler and has fewer dependencies compared to es-main.

require-main-filename

The require-main-filename package helps you get the filename of the main module. While it doesn't directly check if a module is the main module, it can be used in conjunction with other logic to achieve similar results.

module

The built-in Node.js module object can be used to check if a module is the main module by comparing `require.main` with `module`. This is a more manual approach but doesn't require any additional packages.

README

es-main

Test if an ES module is run directly with Node.js. Acts as a replacement for require.main.

use

import esMain from 'es-main';

if (esMain(import.meta)) {
  // Module run directly.
}

why?

It can be useful to have a module that is both imported from other modules and run directly. With CommonJS, it is possible to have a top-level condition that checks if a script run directly like this:

if (require.main === module) {
  // Do something special.
}

With ES modules in Node.js, require.main is not available. Other alternatives like process.mainModule and module.parent are also not defined for ES modules. In the future, there may be an alternative way to do this check (e.g. import.meta.main or a special main export). Until then, this package provides a workaround.