Detect if called through require or directly by command line

if (require.main === module) {
    console.log('called directly');
} else {
    console.log('required as a module');
}

See documentation for this here: https://nodejs.org/docs/latest/api/modules.html#modules_accessing_the_main_module

There is another, slightly shorter way (not outlined in the mentioned docs).

var runningAsScript = !module.parent;

I outlined more details about how this all works under the hood in this blog post.

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