JS Objects are By Reference by default

objectsbyref.js

const a = { name: 'Max', age: 24 };
const b = a;
b.name = 'Barbara';
console.log(b); // { name: 'Barbara', age: 24 }
console.log(a); // { name: 'Barbara', age: 24 } (a.name was overwritten as well by b.name)

// To avoid passing by reference
const foo = { name: 'Max', age: 24 };
const bar = Object.assign({}, foo);
bar.name = 'Barbara';
console.log(bar); // { name: 'Barbara', age: 24 }
console.log(foo); // { name: 'Max', age: 24 }