object.assign vs the spread operator

object assign

const a = { foo: 'foo'};
const b = { bar: 'bar'};
// the wrong way
const result = Object.assign(a, b);

console.log(a)
// { foo: 'foo', bar: 'bar' }
// this is usually bad, we usually don't want to mutate `a` in most cases

// The right ways:
// 1. using Object.assign with an empty hash for the first param:
const result = Object.assign({}, a, b);
console.log(a)
// { foo: 'foo' }

// 2. using the spread operator
const result = {
  foo: 'foo',
  ...b
};
// or
const result = {
  ...a,
  ...b
};

console.log(a)
// { foo: 'foo' }