如何使用基于另一个数组的值过滤对象数组

Question

I have two arrays, first containing objects and second containing ids. I want to return a new array from the first array that has ids from the first array. What is the best and efficient way to do this?

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

For linear time-complexity convert second array in to set and then use 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) 

If you want to keep the order of result array according to the secondArr then first make a object from firstArr and then use map() on 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) 

Answer 2

You can achieve this with .indexOf() or .includes() method

 const firstArr = [{ id: 2, city: 'London' }, { id: 2, city: 'Tokyo' }, { id: 5, city: 'Berlin' }, { id: 10, city: 'Paris' }, { id: 6, city: 'Rome' }]; const secondArr = ['2', '5']; const output = firstArr.filter((r) => { return secondArr.includes(`${r.id}`); }); console.log(output); 

 const firstArr = [{ id: 2, city: 'London' }, { id: 2, city: 'Tokyo' }, { id: 5, city: 'Berlin' }, { id: 10, city: 'Paris' }, { id: 6, city: 'Rome' }]; const secondArr = ['2', '5']; const output = firstArr.filter((r) => { return secondArr.indexOf(`${r.id}`) > -1; }); console.log(output); 

Answer 3

This should do the trick:

secondArr.map(e => firstArr.filter(a => a.id == +e))

I'm using +e to cast the string to an int, might not be the best way but certainly the shortest.

Answer 4

const wantedArr = firstArr.filter(({ id }) => secondArr.includes(`${id}`));