Node functions

The handler for Node functions must be the path to your handler file plus the function to invoke. For example, with the following directory structure:

- src
  - handlers
  - firstHandler.js  => module.exports.myFirstHandler = ...
  - secondHandler.js => module.exports.mySecondHandler = ...
- serverless.yml

Your serverless.yml would look like:

provider:
  runtime: node22
functions:
  first:
    handler: src/handlers/firstHandler.myFirstHandler
  second:
    handler: src/handlers/secondHandler.mySecondHandler

NOTE if you wish to use Typescript, you can do so by transpiling your code locally before deploying it. An example is available here.

ES modules

Node has two module systems:

• CommonJS - modules (default)
• ECMAScript/ES modules - gives a more modern way to reuse your code (docs)

According to the official documentation, to use ES modules you can specify the module type in package.json, as in the following example:

  ...
  "type": "module",
  ...

This then enables you to write your code for ES modules:

export { handle };

function handle(event, context, cb) {
  return {
    body: process.version,
    headers: { "Content-Type": ["text/plain"] },
    statusCode: 200,
  };
}

The use of ES modules is encouraged since they are more efficient and make setup and debugging much easier.

Note that using "type": "module" or "type": "commonjs" in your package.json file will enable or disable some features in Node runtime, such as:

• commonjs is used as the default value
• commonjs allows you to use require/module.exports (synchronous code loading - it basically copies all file contents)
• module allows you to use import/export ES6 instructions (asynchronous loading - more optimized as it imports only the pieces of code you need)

Tip: For a comprehensive list of differences, please refer to the Node.js official documentation.