Deep comparison of two objects

JavaScript
1

Hello Campers,

Can anyone explain me how the solution for deep comparison of two objects works?

Here is the full solution:

function deepEqual(a, b) {
  if (a === b) return true;
  
  if (a == null || typeof a != "object" ||
      b == null || typeof b != "object") return false;

  let keysA = Object.keys(a), keysB = Object.keys(b);

  if (keysA.length != keysB.length) return false;

  for (let key of keysA) {
    if (!keysB.includes(key) || !deepEqual(a[key], b[key])) return false;
  }

  return true;
}

The part that I cannot understand is:

  for (let key of keysA) {
    if (!keysB.includes(key) || !deepEqual(a[key], b[key])) return false;
  }

I will appreciate any help.

2

It is a recursion. Try to find another simple decision. It is complecate to debug and explain.

3

Hi, thanks. I know it is recursion.

What I cannot understand is the flow of the code.

1 Like
4 
!deepEqual(a[key], b[key])) return false;

the function returns opposite of the boolean. It depends. If it is true, returns false and otherwise.Simple checks for both object has other children since both objects has equal size.

5

Thanks! I’ve reviewed the code. Tested it using console.log() to better understand the output and seems like for now it’s clear :slight_smile:

1 Like