修改for..of的两种方式

let obj = {
    a: 'a',
    b: 'b',
    c: 'c'
};
Object.prototype[Symbol.asyncIterator] = function () {
    let index = 0;
    let obj = this;
    return {
        next() {
            if (index < Object.keys(obj).length) {
                return { value: obj[Object.keys(obj)[index++]], done: false };
            } else {
                return { value: undefined, done: true };
            }
        }
    };
};

Object.prototype[Symbol.iterator] = function* () {
    for (let key of Object.keys(this)) {
        yield this[key];
    }
};

for await (const x of obj) {
    console.log(x);
}

const [a, b, c] = obj;
console.log(a, b, c);