Cyclically Rotating a Grid LeetCode solution in JavaScript

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var rotateGrid = function (grid, k) {
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  const m = grid.length;
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  const n = grid[0].length;
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  let startRow = 0;
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  let endRow = m - 1;
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  let startCol = 0;
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  let endCol = n - 1;
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  while (startRow <= endRow && startCol <= endCol) {
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    let currRowStart = startRow;
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    let currRowEnd = endRow;
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    let currColStart = startCol;
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    let currColEnd = endCol;
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    const vals = [];
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    // Top
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    for (let col = currColStart; col <= currColEnd; ++col) {
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      const val = grid[currRowStart][col];
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      vals.push(val);
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    }
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    ++currRowStart;
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    // Right
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    for (let row = currRowStart; row <= currRowEnd; ++row) {
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      const val = grid[row][currColEnd];
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      vals.push(val);
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    }
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    --currColEnd;
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    // Bottom
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    for (let col = currColEnd; col >= currColStart; --col) {
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      const val = grid[currRowEnd][col];
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      vals.push(val);
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    }
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    --currRowEnd;
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    // Left
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    for (let row = currRowEnd; row >= currRowStart; --row) {
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      const val = grid[row][currColStart];
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      vals.push(val);
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    }
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    ++currColStart;
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    const size = vals.length;
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    const remK = k % size;
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    const movedVals = [];
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    for (let i = 0; i < size; ++i) {
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      const movedIdx = (i + remK) % size;
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      movedVals[i] = vals[movedIdx];
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    }
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    let i = 0;
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    currRowStart = startRow;
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    currRowEnd = endRow;
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    currColStart = startCol;
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    currColEnd = endCol;
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    // Top
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    for (let col = currColStart; col <= currColEnd; ++col) {
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      grid[currRowStart][col] = movedVals[i++];
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    }
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    ++currRowStart;
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    // Right
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    for (let row = currRowStart; row <= currRowEnd; ++row) {
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      grid[row][currColEnd] = movedVals[i++];
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    }
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    --currColEnd;
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    // Bottom
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    for (let col = currColEnd; col >= currColStart; --col) {
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      grid[currRowEnd][col] = movedVals[i++];
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    }
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    --currRowEnd;
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    // Left
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    for (let row = currRowEnd; row >= currRowStart; --row) {
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      grid[row][currColStart] = movedVals[i++];
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    }
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    ++currColStart;
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    // update the boundaries for the next layer
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    startRow = currRowStart;
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    endRow = currRowEnd;
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    startCol = currColStart;
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    endCol = currColEnd;
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  }
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  return grid;
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};