Es6中iterator的value改变情况？

let arr = [
    {'zhangsan':18},
]

const iter = arr[Symbol.iterator]()
const one = iter.next()
console.log(one);
one.value['zhangsan'] = 28
console.log(one);
console.log(arr);

输出:

let arr = [
    {'zhangsan':18},
]

const iter = arr[Symbol.iterator]()
const one = iter.next()
console.log(one);
one.value = {'lisi':100}
console.log(one);
console.log(arr);

直接覆盖'zhangsan'这个属性，为什么最后的arr没有改变呢？