Intersection of two arrays in javascript

Question

I want to search in a big array for different id from another array and print all intersections of those two arrays

I want to map through my bigTable and I want to create another array of correspondence, each found element must contain all fields+tableName+tableID like this :

const output = [{ ID: 1234, title: 'title1', TableName: 'loramIpsum', TableId: 11, }, { ID: 98523, title: 'mylasttitle', TableName: 'table2', TableId: 87545, }, { ID: 97766, title: 'mylastdata', TableName: 'table2', TableId: 87545, }, ]

I've create a function but I think there is another best and sample solution, this is my function :

const getResult = (wantedData, bigArray) => { return wantedData.flatMap((id) => bigArray.flatMap((family) => family.Tables.flatMap((table) => { let item = table.myDatas.find((el) => el.ID === id); if (item) { item.Table = table.TableName; item.familyId = family.GridId; return item; } }).filter((result) => result !== undefined) ) ); }; console.log(getResult(wantedData, bigArray))

<script> const wantedData = [1235, 98523, 97766]; const bigArray = [{ bigArrayId: 1111, Tables: [{ TableId: 11, TableName: 'loramIpsum', myDatas: [{ ID: 1234, title: 'title1', }, { ID: 1235, title: 'title2', }, ], }, ], }, { bigArrayId: 674665, Tables: [{ TableId: 87545, TableName: 'table2', myDatas: [{ ID: 98523, title: 'mylasttitle', }, { ID: 24134, title: 'alex', }, { ID: 97766, title: 'mylastdata', }, ], }, ], }, ]; </script>

Any help please ? Can I do it with recursive function ?

I reformatted you question so it is readable and made a snippet. but the snippet gives console errors — mplungjan
– mplungjan, Commented Apr 15, 2022 at 10:21
Thank your for your formatting, yes sometimes it show an error, I still don't know why, When I'm triyng to find in myDatas array I get this error — Duchere
– Duchere, Commented Apr 15, 2022 at 10:25
Change to let item = table.myDatas?.find((el) => el.ID === id); since you do not have myDatas in the last entry — mplungjan
– mplungjan, Commented Apr 15, 2022 at 10:28
I edited my array, now it work's for my example, I want to know if there is another best solutions to refactoration now :) — Duchere
– Duchere, Commented Apr 15, 2022 at 10:31
So you are saying that your code works but you are looking for a better solution? — Christian Vincenzo Traina
– Christian Vincenzo Traina, Commented Apr 15, 2022 at 10:34

A1exandr Belan · Accepted Answer · 2022-04-15 12:36:41Z

I think you need to solve this problem in two steps:

First, create a flat array of tables
Then filter the array by conditions

const bigArray=[{bigArrayId:1111,Tables:[{TableId:11,TableName:"loramIpsum",myDatas:[{ID:1234,title:"title1"},{ID:1235,title:"title2"}]}]},{bigArrayId:674665,Tables:[{TableId:87545,TableName:"table2",myDatas:[{ID:98523,title:"mylasttitle"},{ID:24134,title:"alex"},{ID:97766,title:"mylastdata"}]}]}]; const wantedData = [1235, 98523, 97766]; const flatTables = bigArray.flatMap(({ Tables }) => Tables.flatMap(({ myDatas, TableId, TableName }) => myDatas.map((data) => ({ ...data, TableId, TableName })) )); const result = flatTables.filter(({ ID }) => wantedData.includes(ID)); console.log(result);

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Ben Stephens · Accepted Answer · 2022-04-15 13:25:49Z

I think if you do it something like this you'll be able to map after you've found the right things rather than mapping everything and then filtering that result:

const bigArray = [{ bigArrayId: 1111, Tables: [{ TableId: 11, TableName: 'loramIpsum', myDatas: [{ ID: 1234, title: 'title1', }, { ID: 1235, title: 'title2', }, ], }, ], }, { bigArrayId: 674665, Tables: [{ TableId: 87545, TableName: 'table2', myDatas: [{ ID: 98523, title: 'mylasttitle', }, { ID: 24134, title: 'alex', }, { ID: 97766, title: 'mylastdata', }, ], }, ], }, ]; const wantedData = [1235, 98523, 97766]; const wanted_set = new Set(wantedData); const push_concat = (arr1, arr2) => { for(let i = 0; i < arr2.length; i++) arr1.push(arr2[i]); return arr1; }; const res = bigArray.reduce( (acc, { Tables }) => push_concat(acc, Tables.flatMap(({ TableId, TableName, myDatas }) => myDatas .filter(({ ID }) => wanted_set.has(ID)) .map(({ ID, title }) => ({ ID, title, TableId, TableName })) ) ), [] ); console.log(res);

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