关于javascript:修改数组对象的属性名只修改对象的key不修改value

let arr = [{ name: '张三', year: 18}, {name: '李四', year: 19}] 
let brr = [{ userName: '张三', age: 18}, {userName: '李四', age: 19} ]
 
changeKeys (arr, key) {let newArr = [];
  arr.forEach(item => {let obj = {};
    for (var i = 0; i < key.length; i++) {obj[key[i]] = item[Object.keys(item)[i]]
    }
    newArr.push(obj);
  })
  return newArr;
}
 
let brr= changeKeys (arr, ['userName', 'age']);