JavaScript Nullish Coalescing.js

const data = {
  foo: 'bar',
  falsyValue: false
}

// this one is good
const containerOne = data.foo || 'fallback'
console.log('container one =', containerOne); // container one = bar

// non existed - still "good"
const containerTwo = data.unexisted || 'fallback'
console.log('container two =', containerTwo); // container two = fallback

// this one is WRONG! because falsyValue value is equal to false, so it would lead to a bug
const containerThree = data.falsyValue || 'fallback'
console.log('container three =', containerThree); // container three = fallback, however it should be 'false'

// this is a correct way - using nullish coalescing
// NOTE - that is NOT part of js implementation yet
// const containerFour = data.falsyValue ?? 'fallback'
// console.log('container four =', containerFour); // container three = fallback

// kind of ugly but safe way for a temporarly substitution of nullish coalescing
const containerFive = [undefined, null].includes(data.falsyValue) || 'fallback'
console.log('container five =', containerFive); // container three = fallback

// with || the second operand is evaluated if the first operand is undefined, null, false, 0, NaN or ''.
// with ?? on the other hand limits this list to only undefined and null.

// inspired by https://flaviocopes.com/javascript-nullish-coalescing/