fifel

Stands for "Functional If..Else".

Feature

A helper function gives a functional "if" statement. Gives a unified output for both truthy/falsy branches. "const over let" fans, you are welcome! 😎

Install

npm install fifel

Usage

Basic

if..else example

import { fif } from 'fifel';

const result = fif(
  Math.random() > 0.5,
  () => 'truthy',
  () => 'falsy'
);

if only example

else branch is optional. If you don't need it, you can skip it:

import { fif } from 'fifel';
const result = fif(
  Math.random() > 0.5,
  () => {
    // some logic
    return 'truthy';
  }
);

Advanced

This way, we use const instead of let for the result variable you expect to get. It is more helpful when statements in if and else branches include multiple steps before the result is assigned or even some after that. With fif it is better structured:

import { fif } from 'fifel';
function getSomeFuits(amount = 5) {
  return fif(
    isEnoughInStock(amount),
    () => {
      const result = getFruitsFromStock(amount);
      if (needToRefillStock()) {
        const amountToRefill = getAmountToRefill();
        stickANoteOnTheStock(`Please refill the stock (${amountToRefill} pcs)!`);
      }
      return {
        fromStock: amount,
        fromSupplier: 0,
        full: true
      };
    },
    () => {
      const amountOnStock = getAmountOnStock();
      const fromStock = getFruitsFromStock(amountOnStock);
      stickANoteOnTheStock(`Stock is empty! Please refill!`);
      const fromSupplier = getFruitsFromSupplier(amount - fromStock);
      
      return { 
        fromStock,
        fromSupplier,
        full: fromStock + fromSupplier === amount
      };
    }
  );
}

Within the same logic, using if..else and let result would be less readable and assignment to result could be lost in lines of code.

TypeScript

fif function is typed. You can use it with TypeScript as well. In previous examples, result types are inferred are perfectly inferred.

if..else

import { fif } from 'fifel';
// transport type is inferred as Car | Bike ✅
const transport = fif(
  readyToGo(),
  () => {
    // some logic
    return getCarFromGarage(); // returns Car
  },
  () => {
    return buyBike(); // returns Bike
  }
);

if only

import { fif } from 'fifel';
// transport type is inferred as Car | undefined ✅
const transport = fif(
 readyToGo(),
 () => {
   // some logic
   return getCarFromGarage(); // returns Car
 }
);

License

MIT