CODEWITHSUNDEEP
node.jsmodule
Hubro
Hubro

Reputation: 59323

Can I know, in node.js, if my script is being run directly or being loaded by another script?

I'm just getting started with node.js and I have some experience with Python. In Python I could check whether the __name__ variable was set to "__main__", and if it was I'd know that my script was being run directly. In that case I could run test code or make use of the module directly in other ways.

Is there anything similar in node.js?

Upvotes: 72

Views: 14501

Answers (3)

qiao
qiao

Reputation: 18219

You can use module.parent to determine if the current script is loaded by another script.

e.g.

a.js:

if (!module.parent) {
    console.log("I'm parent");
} else {
    console.log("I'm child");
}

b.js:

require('./a')

run node a.js will output:

I'm parent

run node b.js will output:

I'm child

Upvotes: 100

David Braun
David Braun

Reputation: 5889

The accepted answer is fine. I'm adding this one from the official documentation for completeness:

Accessing the main module

When a file is run directly from Node, require.main is set to its module. That means that you can determine whether a file has been run directly by testing

require.main === module

For a file "foo.js", this will be true if run via node foo.js, but false if run by require('./foo').

Because module provides a filename property (normally equivalent to __filename), the entry point of the current application can be obtained by checking require.main.filename.

Upvotes: 51

Thorsten Lorenz
Thorsten Lorenz

Reputation: 11847

Both options !module.parent and require.main === module work. If you are interested in more details please read my detailed blog post about this topic.

Upvotes: 11

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