Comparing two array and create a new array with matched one by keeping duplicates (javascript)

Question

I have two arrays. I want to compare them and make a new array out of it with matched values but I want to keep duplicate values as well.

Like:

let array1 = [1, 3, 3, 3]
let array2 = [{id:1}, {id:2},{id:3}]

array1 = array1.filter(e1 => array2.some(e2 => e2.id === e1))
array2 = array2.filter(e1 => array1.some(e2 => e2 === e1.id))

output:

array2 = [{id:1}, {id:3}]

But I want to get the duplicate as well.

Desired output

array2=[{id:1}, {id:3}, {id:3}, {id:3}] //as array1 has 3 multiple time

Answer 1

We can use Array.filter() and Array.map() to change data of array1,then assign it to array2

let array1 = [1, 3, 3, 3]
let array2 = [{id:1}, {id:2},{id:3}]

array2 = array1.filter(e1 => array2.some(e2 => e2.id === e1)).map(e => ({'id':e}))

console.log(array2)

---

Update:without assign value from array1 to array2

let array1 = [1, 3, 3, 3]
let array2 = [{id:1}, {id:2},{id:3}]

array1 = array1.filter(e1 => array2.some(e2 => e2.id === e1))
array2 = array2.filter(e1 => array1.some(e2 => e2 === e1.id))

array1 = array1.reduce((a,v) =>{
  a[v] = a[v]??0
  a[v] += 1
  return a
},{})

array2 = array2.reduce((a,v) =>{
  let cnt = array1[v.id]
  for(let i=0;i<cnt;i++){
   a.push({...v})
  }
  return a
},[])  

console.log(array2)