Practical Microservices

Arrow Functions

Arrow functions give us a shorthand for defining functions that we use mostly when defining inline functions. Here is an example of one from the book, taken from the identity component’s handlers:

video-tutorials/src/components/identity/index.js

return {
  Register: command => {
    const context = { 
      messageStore: messageStore,
      command,
      identityId: command.data.userId
    }

    return Bluebird.resolve(context)
      .then(loadIdentity)
      .then(ensureNotRegistered)
      .then(writeRegisteredEvent)
      .catch(AlreadyRegsiteredError, () => {})
  }
}

We’re defining an object literal with key Register whose value is a function. This function takes one parameter, namely command. Previously we would have had to write this function ...