non-writable

Question

What does the code snippet to the right output by console.log?

Snippet

const a = {}
Object.defineProperty(a, 'foo1', {
  value: 1
})
const b = Object.create(a)
b.foo2 = 1

console.log(b.foo1)
console.log(b.foo2)

b.foo1 = 2
b.foo2 = 2


console.log(b.foo1)
console.log(b.foo2)

Source

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