How to combine 2 multidimensional arrays replacing some of array1's element with the one from arrray2 using Google Apps Script?

I’ve been trying to get this one done, without any success.

This is data to be placed where there is no formula. So, the idea is to merge these two arrays and place it at once.

array1 = 
[
 ["item1","","","details1"], 
 ["item2","","","details2"], 
]

This array contains formulas grabbed from the destination range where the incoming data will be placed, but since the formulas are needed,

array2 = 
[
 ["","=iferror(VLOOKUP(A63,'Client List'!$A$1:$S,19,0),"")","=iferror(if(B63="Agency", 'Reference Info'!$C$7, VLOOKUP(A63,'Client List'!$A$1:$T,20,0)),"")",""], 
 ["","=iferror(VLOOKUP(A64,'Client List'!$A$1:$S,19,0),"")","=iferror(if(B64="Agency", 'Reference Info'!$C$7, VLOOKUP(A64,'Client List'!$A$1:$T,20,0)),"")",""]
]

Expected Result

array2 = 
[
 ["item1","=iferror(VLOOKUP(A63,'Client List'!$A$1:$S,19,0),"")","=iferror(if(B63="Agency", 'Reference Info'!$C$7, VLOOKUP(A63,'Client List'!$A$1:$T,20,0)),"")","details1"], 
 ["item2","=iferror(VLOOKUP(A64,'Client List'!$A$1:$S,19,0),"")","=iferror(if(B64="Agency", 'Reference Info'!$C$7, VLOOKUP(A64,'Client List'!$A$1:$T,20,0)),"")","details2"]
]

This is my attempt, but I can’t seem to get to the bottom of it:

 let finalRowValues = []
  for (let a = 0; a < array2.length; a++) {
    for (let n = 0; n < array1.length; n++) {
      array2[a].forEach(function(value, j){
        if(value == '' && array1[n][j] != ''){
          finalRowValues.push(array1[n][j])
        } else {
          finalRowValues.push(value)
        }
      })
    }
  }

>Solution :

This is one of the way’s to do it.

const array1 = 
[
 ["item1","","","details1"], 
 ["item2","","","details2"], 
]

const array2 = 
[
 ["",`=iferror(VLOOKUP(A63,'Client List'!$A$1:$S,19,0),"")`,`=iferror(if(B63="Agency", 'Reference Info'!$C$7, VLOOKUP(A63,'Client List'!$A$1:$T,20,0)),"")`,""], 
 ["",`=iferror(VLOOKUP(A64,'Client List'!$A$1:$S,19,0),"")`,`=iferror(if(B64="Agency", 'Reference Info'!$C$7, VLOOKUP(A64,'Client List'!$A$1:$T,20,0)),"")`,""]
]

const result = array1.map((arr, i) => {
  const [place1, place2, place3, place4] = arr
  if(place2 == ""){
    return [place1, array2[i][1], array2[i][2],place4]
  } else {
    return arr
  }
})

console.log(result)