https://github.com/tschaub/es-main

Test if an ES module is run directly (require.main replacement)
https://github.com/tschaub/es-main

Last synced: 7 days ago
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Test if an ES module is run directly (require.main replacement)

• Host: GitHub
• URL: https://github.com/tschaub/es-main
• Owner: tschaub
• Created: 2020-02-19T22:49:19.000Z (almost 5 years ago)
• Default Branch: main
• Last Pushed: 2024-10-21T17:25:48.000Z (3 months ago)
• Last Synced: 2024-10-22T07:27:00.835Z (3 months ago)
• Language: JavaScript
• Homepage: https://www.npmjs.com/package/es-main
• Size: 258 KB
• Stars: 85
• Watchers: 4
• Forks: 6
• Open Issues: 0
• Metadata Files:
  • Readme: readme.md

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README

        
# es-main

Test if an [ES module](https://nodejs.org/api/esm.html) is run directly with Node.js.  Acts as a replacement for `require.main`.

## use

```js

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:

```js

if (require.main === module) {

  // Do something special.

}

```

With ES modules in Node.js, `require.main` is [not available](https://nodejs.org/dist/latest-v14.x/docs/api/esm.html#esm_no_require_exports_module_exports_filename_dirname).  Other alternatives like `process.mainModule` and `module.parent` are also not defined for ES modules.  In the future, there may be [an alternative way](https://github.com/nodejs/modules/issues/274) to do this check (e.g. `import.meta.main` or a special `main` export).  Until then, this package provides a workaround.