Within a nest.js service: I have a service method that takes an error code and outputs a message which is later on displayed to the user. The following method is a shortened version of it:

  getGenericErrorMessage(input: string): string {
    const errorMessages = {
      unknownError: 'An unknown error occurred. ',
      noResponse: 'The Application did not send a response. ',
    };
    return errorMessages[input] || errorMessages['unknownError'];
  }

Is there a way to get intellisense for valid function parameters that are defined as keys in errorMessages? Or is there any way I can restructure my code to archive this?

CodePudding user response：

You can move errorMessages out then use keyof like this:

const errorMessages = {
  unknownError: 'An unknown error occurred. ',
  noResponse: 'The Application did not send a response. ',
};

function getGenericErrorMessage(input: keyof typeof errorMessages): string {
  return errorMessages[input]; // <--- // `input` must be `unknownError` or `noResponse`, so you can remove the fallback
}

If you want to discuss further, leave a comment below