元素分组

一、认识

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二、实现

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实现

function groupBy(array, keyFn) {
  return array.reduce((result, item) => {
    const key = typeof keyFn === 'function' ? keyFn(item) : item[keyFn];
    if (!result[key]) {
      result[key] = [];
    }
    result[key].push(item);
    return result;
  }, {});
}

测试

// 示例 1：按数字的奇偶性分组
const numbers = [1, 2, 3, 4, 5, 6];
const groupByOddEven = groupBy(numbers, num => (num % 2 === 0 ? 'even' : 'odd'));
console.log('按奇偶性分组：', groupByOddEven);
// 输出结果：{ odd: [ 1, 3, 5 ], even: [ 2, 4, 6 ] }

// 示例 2：按对象属性分组
const persons = [
  { name: 'Alice', age: 25 },
  { name: 'Bob', age: 30 },
  { name: 'Charlie', age: 25 }
];
const groupByAge = groupBy(persons, 'age');
console.log('按年龄分组：', groupByAge);
// 输出结果：{ '25': [ { name: 'Alice', age: 25 }, { name: 'Charlie', age: 25 } ], '30': [ { name: 'Bob', age: 30 } ] }