JavaScript如何用数组的flat方法展平嵌套

const arr = [1, [2, [3, [4, 5]]]];

// 默认展平一层
console.log(arr.flat()); // [1, 2, [3, [4, 5]]]

// 展平两层
console.log(arr.flat(2)); // [1, 2, 3, [4, 5]]

// 展平所有层级
console.log(arr.flat(Infinity)); // [1, 2, 3, 4, 5]

function flatten(arr, depth = 1) {
  return arr.reduce((acc, val) => {
    if (Array.isArray(val) && depth > 0) {
      return acc.concat(flatten(val, depth - 1));
    } else {
      return acc.concat(val);
    }
  }, []);
}

const arr = [1, [2, [3, [4, 5]]]];
console.log(flatten(arr, Infinity)); // [1, 2, 3, 4, 5]

function flatten(arr) {
  return arr.reduce((acc, val) => acc.concat(val), []);
}

const arr = [1, [2, 3], [4, 5]];
console.log(flatten(arr)); // [1, 2, 3, 4, 5]

function flatten(arr) {
  return [].concat.apply([], arr);
}

const arr = [1, [2, 3], [4, 5]];
console.log(flatten(arr)); // [1, 2, 3, 4, 5]

const users = [
  { name: 'Alice', interests: ['reading', 'music'] },
  { name: 'Bob', interests: ['sports', ['hiking', 'swimming']] },
  { name: 'Charlie', interests: ['coding'] }
];

// 获取所有用户的兴趣爱好
const allInterests = users.map(user => user.interests).flat(Infinity);
console.log(allInterests); // ["reading", "music", "sports", "hiking", "swimming", "coding"]