Comparing between values of 2 arrays not working in Javascript

Question

im trying to compare between two arrays, whether they have same value at same place, same values at different places or not the same at all. after comparing I want to enter a char to a third array to indicate the result. my code doesnt work for some reason... its not comparing correctly. what am i doing wrong?

var numInput = [1,2,3,4];
var numArr = [2,5,3,6];
var isBp;
var i,j;
  for ( i = 0; i < 4; i++)
   {
     if (numInput[i] == numArr[i])
     {  isBP[i] = "X"; }
     else
     {
       for ( j = 0; j<4; j++)
       {
         if (numInput[i] == numArr[j])
          {isBP[i] = "O";}
         else
          { isBP[i] = "-"; }
       }

     }

     }

the result should be:

isBP = [O,-,X,-]

Does this answer your question? [How to compare arrays in JavaScript?](https://stackoverflow.com/questions/7837456/how-to-compare-arrays-in-javascript) — A. Meshu, Aug 23 '20 at 18:53
Have you considered using [indexOf](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/indexOf) for this? — ray hatfield, Aug 23 '20 at 18:55
If you could explain your expected result with this example, we could discuss, what to do. — Nikolaus, Aug 23 '20 at 18:58

charlietfl · Answer 1 · 2020-08-23T19:32:21.233

0

This is a fairly simple array map operation. If I understand correctly you want an X when they match and an O when they don't and that doesn't exist at all and - when it exists but at different location

var numInput = [1,2,3,4];
var numArr = [2,5,6,4];

var isBP = numInput.map((n,i) => ((n === numArr[i] ? 'X' :  numArr.includes(n) ? '-': 'O')))

console.log(isBP)

edited Aug 23 '20 at 19:32

answered Aug 23 '20 at 19:00

charlietfl

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nearly, but you're missing the case for "exists in the other set at a different location", which, I think, should get a "-" – daf Aug 23 '20 at 19:23
OP is after two things: whether it’s there at all, and if so whether it’s at the same index. – ray hatfield Aug 23 '20 at 19:24
@rayhatfield Yup...completely missed that case – charlietfl Aug 23 '20 at 19:28

score 0 · Answer 2 · answered Aug 23 '20 at 19:24

It looks like you'd like to output:

X if the numbers at the same indexes are equal
- if they are not equal at the same indexes, but the number is found elsewhere
O if the number from the first array doesn't exist in the second at all

if so:

var a1 = [1, 2, 3];
var a2 = [1, 3, 4];

var result = a1.map((n, i) => {
  var match = a2.indexOf(n);
  if (match === i) {
    return "X"
  } else if (match > -1) {
    return "O";
  } else {
    return "-";
  }
});

console.log(result); // prints [ 'X', '-', 'O' ]

Comparing between values of 2 arrays not working in Javascript

2 Answers2