11 - Creating Node.js modules

Creating Node.js modules

Node.js modules are one kind of package which can be published to npm. When you create a new module, you want to start with the package.json file.

You can use npm init to create the package.json. It will prompt you for values for the package.json fields. The two required fields are name and version. You'll also want to have a value for main. You can use the default, index.js.

If you want to add information for the author field, you can use the following format (email and web site are both optional):

Your Name <email@example.com> (http://example.com)

Once your package.json file is created, you'll want to create the file that will be loaded when your module is required. If you used the default, this is index.js.

In that file, add a function as a property of the exports object. This will make the function available to other code.

exports.printMsg = function() {
  console.log("This is a message from the demo package");
}

Test:

1. Publish your package to npm
2. Make a new directory outside of your project and cd into it
3. Run npm install <package>
4. Create a test.js file which requires the package and calls the method
5. Run node test.js. The message should be output.