SOURCE

const obj = {
    toString() { // 3
        return 1
    },
    valueOf() { // 2
        return 2
    },
    [Symbol.toPrimitive]() { // 1
        return 3
    }
}

console.log(obj + 1)


const a = {}

const func = function d(){}

a[func] = 33333


console.log(a)

console.log(Object.keys(a), d)