Deep equals on 2 variables where a is compared with b

deep.js

function deepEquals(a, b) {
  if(a === b) {
    return true;
  }
  
  if(a && b && typeof a === 'object' && typeof b === 'object' && Object.keys(a).length === Object.keys(b).length && Array.isArray(a) === Array.isArray(b)) {
    for(let key in a) {
      if(key in b) {
        if(!deepEquals(a[key], b[key]) {
           return false;
        }
      } else {
        return false;
      }
    }
    return true;
  }
  
  return false;
}