When you want to utilize a rust like Result structure, because it helps you to organize the code better.

Example.ts

function calc(a: number): Result<string, string> {
  if (a !== 0) {
    return Some("thing")
  } else {
    return Err("a cannot be zero")
  }
}

let result = calc(0)
if(result.error) {
  console.error(result.error)
} else {
  console.log(result.value)
}

Result.ts

class Result<T, E> {
    value: T | null
    error: E | null
}

function Ok<T, E>(val: T): Result<T, E> {
    return {
        value: val,
        error: null
    }
}

function Err<T, E>(err: E): Result<T, E> {
    return {
        value: null,
        error: err
    }
}

export { Result, Ok, Err }