Question

What's the output?

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

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

• A: Hello
• B: Hey!
• C: undefined
• D: ReferenceError
• E: TypeError

Answer 1

Answer: A

In JavaScript, all objects interact by reference when setting them equal to each other.

First, variable c holds a value to an object. Later, we assign d with the same reference that c has to the object.

When you change one object, you change all of them.