Javascript中的对象属性是有序的吗

const obj = {
100: 100,
'2': 2,
12: 12,
'0': 0
}
// 下面打印的结果顺序都是 ['0', '2', '12', '100']
console.log(Object.keys(obj))
console.log(Object.getOwnPropertyNames(obj))
console.log(Reflect.ownKeys(obj))
for (const key in obj) {
console.log('key', key)
}

const obj = {
a: 'a',
};
obj.b = 'b';
setTimeout(() => {
obj.c = 'c';
});
obj.d = 'd';
// 下面打印的结果顺序都是 `[ 'a', 'b', 'd' ]`
console.log(Object.keys(obj));
console.log(Object.getOwnPropertyNames(obj));
console.log(Reflect.ownKeys(obj));
for (const key in obj) {
console.log('key: ', key);
}

const obj = {
[Symbol('a')]: 'a',
[Symbol.for('b')]: 'b',
};
obj[Symbol('c')] = 'c';
console.log(Object.keys(obj)); // []
console.log(Object.getOwnPropertyNames(obj)); // []
console.log(Reflect.ownKeys(obj)); // [ Symbol(a), Symbol(b), Symbol(c) ]
for (const key in obj) {
console.log('key: ', key); // 没有输出
}
console.log(Object.getOwnPropertySymbols(obj)); // [ Symbol(a), Symbol(b), Symbol(c) ]

const obj = {
100: 100,
0: 0,
a: 'a',
[Symbol('a')]: 'a',
};
obj[Symbol.for('b')] = 'b';
obj.b = 'b';
console.log(Object.keys(obj)); // [ '0', '100', 'a', 'b' ]
console.log(Object.getOwnPropertyNames(obj)); // [ '0', '100', 'a', 'b' ]
console.log(Reflect.ownKeys(obj)); // [ '0', '100', 'a', 'b', Symbol(a), Symbol(b) ]
for (const key in obj) {
console.log('key: ', key); // '0' '100' 'a' 'b'
}

console.log(Object.getOwnPropertySymbols(obj)); // [ Symbol(a), Symbol(b) ]