SOURCE

const obj = {
    name: 'zs',
    age: 18,
    [Symbol('secert')]: '秘密'
}

Object.prototype[Symbol.iterator] = function () {
    let _this = this
    const keys = Reflect.ownKeys(_this)
    let index = 0
    return {
        next() {
            if(index<keys.length) {
                return { value: _this[keys[index++]], done: false }
            } else {
                return { value: undefined, done: true }
            }
        }
    }
}

for (value of obj) {
    console.log(value)
}