SOURCE

function Child() {}
Child.prototype = new Father()
console.log(new Father(), 'new')

let child = new Child()
let value = 'a'
Object.defineProperty(child, 'a', {
    enumerable: true,
    configurable: true,
    set(a) {
        value = a
    },
    get() {
        return value
    }
})

console.log(child, 'child')

function Father () {
    this.b = 'b'
}

console.log('b' in child)

for (let key in child) {
    console.log(key, 'for-in')
}

console.log(child.hasOwnProperty('a'), 'hasOwnProperty-a')
console.log(child.hasOwnProperty('b'), 'hasOwnProperty-b')
delete child.a
console.log(child)