js 获取数组键

const arr = ['a', 'b', 'c', 'd'];
const keys = arr.keys();

for (const key of keys) {
  console.log(key); // 输出: 0 1 2 3
}

const arr = ['a', 'b', 'c', 'd'];
const keysArray = [...arr.keys()];
console.log(keysArray); // 输出: [0, 1, 2, 3]

const objArr = [
  { id: 1, name: 'Alice' },
  { id: 2, name: 'Bob' },
  { id: 3, name: 'Charlie' }
];

const ids = objArr.map(obj => obj.id);
console.log(ids); // 输出: [1, 2, 3]