presult

presult is a super lightweight, type-safe library for handling result types. It provides an alternative to try-catch with just two classes to handle results: Ok and Err.

Usage

presult introduces two functions sResult and asResult. These functions return instances of either the Err or Ok class, depending if an error is thrown or not.

sResult Function

Use the sResult function when executing a synchronous task that may fail. Simply pass in the function you want to call into sResult, and receive an instance of the Ok class if the function does not fail, and the Err class otherwise.

function syncFn(userId: number) {
  if (userId <= 0) {
    throw new Error("user ID must be greater than zero");
  }

  return `hello user ${userId}`;
}

const result = sResult(syncFn);
if (result.error) {
  console.log(result.message); // prints error message to screen
}

console.log(result.message); // prints hello user message to screen

asResult Function

Use the asResult function when executing asynchronous tasks that may fail. Pass in the async function as an argument to asResult, and receive an instance of the Ok class if the function does not fail, and the Err class otherwise.

async function asyncFn(userId: number) {
  return await db.User.findById(userId).returning("users.id");
}

const result = await asResult(asyncFn);
if (result.error) {
  console.log(result.message); // prints database error message to screen
}

console.log(result.message); // prints user id to screen

Err Class

The Err class contstructor takes in a mandatory string representing an error message as the first parameter and a second optional number parameter, representing the status of the error. This could be useful to send status codes like 404 or 500.

Ok Class

The Ok class takes in a generic type T, which will be used to correctly type the message field when constructed. The constructor takes in only one parameter of type T and assigns it to the message field, sets the ok field to true and the error field to false.