Javascript ES6 将对象数组映射到 Set 或按不同属性过滤掉

Question

我有一个包含名称和年龄属性的对象数组，我想过滤掉数组中不同年龄的集合，所以我可以做类似的事情

function distinctAges() {
    const guests = [
          {name: 'Kiley', age: 24}, 
          {name: 'Tom', age: 36}, 
          {name: 'Jason', age: 67},
          {name: 'Mike', age: 24},
          ...];

    let ageSet = new Set();
    guests.foreach(g => ageSet.add(g.age));
    return ageSet;
}

有没有像 Distinct 操作一样不使用 Set 数据类型？如果使用 Set，是否可以将转换写在一行中？

Answer 1

集合是 JS 当前获取不同值数组的方式。您可以将一个对象数组映射到一个值数组，创建一个集合，然后传播回一个数组:

const distinctBy = (prop, arr) => [...new Set(arr.map(o => o[prop]))]

const guests = [{"name":"Kiley","age":24},{"name":"Tom","age":36},{"name":"Jason","age":67},{"name":"Mike","age":24}]

const result = distinctBy('age', guests)

console.log(result)

为了使其更通用，您可以将 prop 替换为谓词函数:

const distinctBy = (predicate, arr) => [...new Set(arr.map(predicate))]

const guests = [{"name":"Kiley","age":24},{"name":"Tom","age":36},{"name":"Jason","age":67},{"name":"Mike","age":24}]

const result = distinctBy(o => o.age, guests)

console.log(result)