Object Referencing Questions Javascript

#javascript #flashcards

Objects Javascript questions

Q11. What's the Output? Object Referencing

let c = { greeting: "Hey!" };
let d;
d = c; 

c.greeting = "Hello";
console.log(d.greeting);

?

Answer

let c = { greeting: "Hey!" };
let d;
d = c; // object is refered

c.greeting = "Hello";
console.log(d.greeting); // Hello

Objects are not copied they are referenced

Q12. What's the output? Object Referencing

console.log({ a: 1 } == { a: 1 }); 
console.log({ a: 1 } === { a: 1 });

?

Answer

console.log({ a: 1 } == { a: 1 }); // false
console.log({ a: 1 } === { a: 1 }); // false

Objects are only equal when they are referencing the same object
As both objects are declared separately they are not the same object & therefore not equal

Q13. What's the output? Object Referencing

let person = { name: "Lydia" };
const members = [person];

person = null;
console.log(members); 

person.name = null;
console.log(members);

?

Answer

let person = { name: "Lydia" };
const members = [person];

person = null;
console.log(members); // [ { name: "Lydia" } ]

person.name = null;
console.log(members); // [ { name: null } ]

Q14. What's the output? Object Referencing

const value = { number: 10 };

const multiply = (x = { ...value }) => {
	console.log((x.number *= 2));
};

multiply(); 
multiply();
multiply(value); 
multiply(value);

?

Answer

const value = { number: 10 };

const multiply = (x = { ...value }) => {
	console.log((x.number *= 2));
};

multiply(); // 20
multiply(); // 20
multiply(value); // 20
multiply(value); // 40