findTheNextPerfectSquare.js

function findNextSquare(sq) {
  // Return the next square if sq is a perfect square, -1 otherwise 
  
  // Declaring variables at the top (older style) 
  let square;
  let nextSquare;
  
  // Check if the square root is a whole number. 
  // The modulo operator (%) returns the remainder. 
  // If a number divided by 1 has 0 remainder, it's an integer. 
  if (Math.sqrt(sq) % 1 === 0) {
    square = Math.sqrt(sq);   // Calculate the root (e.g., if sq is 121, square is 11)
    nextSquare = square + 1;  // Increment the root (11 becomes 12)
  } else {
      return -1; // Early exit if it's not a perfect square
  }
  
  // Multiply the next root by itself to get the final answer
  return nextSquare * nextSquare; 
}




/** 
Using Number.isInteger() for a more readable check
*/
function findNextSquare(sq) {
  // 1. Calculate the root once to avoid doing the math twice
  const root = Math.sqrt(sq);

  // 2. Guard Clause: If the root isn't an integer, we know 'sq' wasn't a perfect square.
  // Number.isInteger() is cleaner and more readable than (root % 1 === 0)
  if (!Number.isInteger(root)) {
    return -1;
  }

  // 3. Return the square of the next number
  // The '**' operator raises the left operand to the power of the right operand
  return (root + 1) ** 2;
}