Given an array, check to see if at least one of its diagonals have the same values

checkArrayDiagonals.js

let myArr = [1,2,3,4,
             4,0,4,4,
             7,0,1,4,
             4,4,4,1],
    
    myArr2 = [1,2,3,4,
              4,1,4,4,
              7,0,1,4,
              4,4,4,1];

function checkDiagonals(arr) {
  // Check if array is a perfect square
  if (!Number.isInteger(Math.sqrt(arr.length))) {
    return false;
  }
  
  let sqrt = Math.sqrt(arr.length);
  let leftDiag = arr[0];
  let rightDiag = arr[sqrt - 1]; 
  
  for(let i = 1; i < sqrt; i++) {
    let nextLeft = arr[((sqrt * i) + i)];
    let nextRight = arr[((sqrt - 1) * (i + 1))];
    
    // Check if current left and right diagonal value match the next value in respective diagonal
    if (leftDiag !== nextLeft && rightDiag !== nextRight) {
      return false;
    };
    
  // Reassign each value with the next value in the diagonal
  leftDiag = nextLeft;
  rightDiag = nextRight; 
  
  };
  return true;
}

checkDiagonals(myArr); // false
checkDiagonals(myArr2); // true