(JavaScript) || and && short circuiting / Nullish

// Short Circuiting (&& and ||)

'use strict';

 

// Use ANY data type, return ANY data type,

// short-circuiting

// If the first value is truthy value, then immediately return that value

 

// OR circuiting returns the first truthy value of all the operands or the last value if all the operands are falsy

// AND operand will return first falsy value or the last value if all the operands are truthy

 

// Usually use OR operator to set a default value then use AND operand to execute the second operand

// If the first one is truthy one

 

console.log('---------------------------------------OR-----------------------------------');

 

console.log(3 || 'Hongsik');    // 3

console.log('' || 'Hongsik');   // Hongsik

console.log(true || 0);         // true

console.log(undefined || null); // null

 

console.log(undefined || 0 || '' || 'Hello' || 23 || null);   // Hello

 

const guests1 = restaurant.numGuests ? restaurant.numGuests : 10;

console.log(guests1);

 

const guests2 = restaurant.numGuests || 10;              // Set default value

console.log(guests2);

 

console.log('---------------------------------------AND-----------------------------------');

console.log(0 && 'Hongsik');

console.log(7 && 'Hongsik');

 

console.log('Hello' && 23 && null && 'jonas');               // NULL

 

if (restaurant.orderPizza) {

  restaurant.orderPizza('mushrooms', 'spinach');

}

 

restaurant.orderPizza && restaurant.orderPizza('mushrooms', 'spinach');         // If orederPizza funtion exists in restaurant,

                                                                                // then, call orderPizza method. && circuiting

 

/// Nullish: null and undefined (NOT 0 or '')

const guestCorrect = restaurant.numGuess ?? 10;

console.log(guestCorrect);