What's missing in this code?
// Check if array has sub-array of 3 items
// where the 1st and 3rd are the same but
// both different from the 2nd, e.g., [1, 2, 1]
// hasBoomerang([3, 6, 3, 6, 1]); // true - [3, 6, 3]
// hasBoomerang([3, 1, 1, 6, 7]); // false
// hasBoomerang([5, 4, 7, 0, 7]); // true - [7, 0, 7]
// hasBoomerang([2, 0, 3, 3, 3]); // false
function hasBoomerang(arr) 
  const pair = [];
  for (const num of arr) 
    pair.push(num);
    if (pair
 === 3) 
      const [a, b, c] = pair;
      if (
) 
        return true;
      }
      pair.
;
    }
  }
  return false;
}
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