Available Captures for Rook LeetCode solution in JavaScript

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var numRookCaptures = function (board) {
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  const r = board.length;
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  const c = board[0].length;
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  let res = 0;
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  const dir = [
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    [0, 1],
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    [0, -1],
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    [1, 0],
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    [-1, 0],
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  ]; // all the 4 possible directions
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  let rook = [];
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  // finding the rook's position
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  for (let i = 0; i < r; i++) {
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    for (let j = 0; j < c; j++) {
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      if (board[i][j] === "R") {
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        rook = [i, j];
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        break;
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      }
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    }
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  }
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  // traversing all the 4 directions
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  for (let [x, y] of dir) {
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    res += helper(x, y, rook[0], rook[1]);
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  }
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  return res;
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  function helper(x, y, i, j) {
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    let newX = x + i;
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    let newY = y + j;
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    let attack = 0;
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    while (newX < r && newY < c && newX >= 0 && newY >= 0) {
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      if (board[newX][newY] === "p") {
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        attack++;
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        break; // break because Rook can't attack more than one pawn in same direction
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      } else if (board[newX][newY] === "B") {
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        break;
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      }
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      // keep moving towards the same direction
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      newX += x;
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      newY += y;
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    }
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    return attack;
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  }
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};