Javascript：查找数组中对某个键具有特定值的所有元素

Question

I have the following Javascript arrays:

ARRAY ONE:
[ TextRow { v_id: 3000 },
  TextRow { v_id: 3001 },
  TextRow { v_id: 3002 } ]

ARRAY TWO:
[ TextRow {
      s_id: 'S001',
      v_id: 3000,
      type: 'control' },
  TextRow {
      s_id: 'S002',
      v_id: 3001,
      type: 'mut' },
  TextRow {
      s_id: 'S003',
      v_id: 3001,
      type: 'mut' },
  TextRow {
      s_id: 'S005',
      v_id: 3001,
      type: 'control' },
  TextRow {
      s_id: 'S008',
      v_id: 3002,
      type: 'mut' } ]

For each element in Array One, I would like to get an array of all the elements in Array Two, where the v_id equals the v_id in array one. For example, for v_id = 3001, I would like to get all the elements in array two where the v_id = 3001 in a separate array. However, I am not sure what is the best way to do this task and whether Javascript already has some existing functions that can help me do this. I am asking this since my Array Two has over 1000 elements and I want to know if there is an efficient way to do this instead of just iterating through elements of the array with a nested for loop. Any insights are appreciated.

Answer 1

You can do a.forEach (or.map) on ARRAY_ONE, then a.filter on ARRAY_TWO to get the matching elements.

I've added a getMatches function to make the logic a little more clear.

 const ARRAY_ONE = [ { v_id: 3000 }, { v_id: 3001 }, { v_id: 3002 } ]; const ARRAY_TWO = [ { s_id: 'S001', v_id: 3000, type: 'control' }, { s_id: 'S002', v_id: 3001, type: 'mut' }, { s_id: 'S003', v_id: 3001, type: 'mut' }, { s_id: 'S005', v_id: 3001, type: 'control' }, { s_id: 'S008', v_id: 3002, type: 'mut' } ]; function getMatches(v_id, array) { return array.filter(el => el.v_id === v_id); } const result = ARRAY_ONE.map(v => { return { array_one_id: v.v_id, matches: getMatches(v.v_id, ARRAY_TWO) }; }); console.log("Result:", result);

Answer 2

You can iterate over the first array with the.forEach( ) method.

Then, you can use the.filter( ) method on the array 2 as the callback function for the forEach.

you should have something like that:

arrayOne.forEach( elmArr1 => arrayTwo.filter( elmArr2 => elmArr1.v_id == elmArr2.v_id ) )

Answer 3

If you want to filter without grouping:

 const firstArray = [ { v_id: 3000 }, { v_id: 3001 }, { v_id: 3002 } ]; const secondArray = [ { s_id: 'S001', v_id: 3000, type: 'control' }, { s_id: 'S002', v_id: 3001, type: 'mut' }, { s_id: 'S003', v_id: 3001, type: 'mut' }, { s_id: 'S005', v_id: 3001, type: 'control' }, { s_id: 'S008', v_id: 3002, type: 'mut' } ]; const result = secondArray.filter(f=> firstArray.some(s=> s.v_id == f.v_id)); console.log(result);

If you want group items by key, then it can be done using reduce method:

 const firstArray = [ { v_id: 3000 }, { v_id: 3001 }, { v_id: 3002 } ]; const secondArray = [ { s_id: 'S001', v_id: 3000, type: 'control' }, { s_id: 'S002', v_id: 3001, type: 'mut' }, { s_id: 'S003', v_id: 3001, type: 'mut' }, { s_id: 'S005', v_id: 3001, type: 'control' }, { s_id: 'S008', v_id: 3002, type: 'mut' } ]; const keys = firstArray.reduce((a, {v_id}) => { a[v_id] = a[v_id] || 1; return a; }, {}); const allKeys = secondArray.reduce((a, {s_id, v_id, type}) => { a[v_id] = a[v_id] || {values: []}; a[v_id].values.push({s_id, v_id, type}); return a; }, {}) Object.keys(allKeys).forEach(k=>{ if(.keys;hasOwnProperty(k)) delete allKeys[k]. }) console;log(allKeys);