javascript - 如何基于另一个数组中的值过滤对象数组

Question

我有两个数组，第一个包含对象，第二个包含id。我想从第一个数组返回一个新数组，该数组具有第一个数组的ID。最佳和有效的方法是什么？

const firstArr = [{id: 1, city: London}, {id: 5, city: 'Berlin'}, {id: 10, city: 'Paris'}, {id: 2, city: 'Rome'}]

const secondArr = ['2', '5']

const wantedArr = [{id: 2, city: 'Rome'}, {id: 5, city: 'Berlin'}]

Answer 1

对于线性时间复杂度，将第二个数组转换为set，然后使用Set.prototype.has

const firstArr = [{id: 1, city: 'London'}, {id: 5, city: 'Berlin'}, {id: 10, city: 'Paris'}, {id: 2, city: 'Rome'}]
const secondArr = ['2', '5'];

let set = new Set(secondArr);
const res = firstArr.filter(x => set.has(String(x.id)));

console.log(res)

如果要根据 secondArr保持结果数组的顺序，则首先从 firstArr中创建一个对象，然后在 map()上使用 secondArr

const firstArr = [{id: 1, city: 'London'}, {id: 5, city: 'Berlin'}, {id: 10, city: 'Paris'}, {id: 2, city: 'Rome'}]
const secondArr = ['2', '5'];

const obj = firstArr.reduce((ac,a) => (ac[a.id] = a,ac), {});

const res = secondArr.map(x => obj[x]);
console.log(res)