Number of Closed Islands LeetCode solution in JavaScript

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/**
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 * @param {number[][]} grid
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 * @return {number}
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 */
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var closedIsland = function (grid) {
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  let rows = grid.length;
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  let cols = grid[0].length;
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  let islandCount = 0; // Initial island count
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  // For Quick Response
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  if (rows <= 2 || cols <= 2) return islandCount;
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  for (let i = 0; i <= rows - 1; i++) {
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    for (let j = 0; j <= cols - 1; j++) {
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      /*
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                If land was found on the border, it can never be enclosed by water.
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                So, mark the all the adjacent land across grid as visited.
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            */
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      if (
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        grid[i][j] === 0 &&
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        (i == 0 || j == 0 || i == rows - 1 || j == cols - 1)
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      ) {
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        dfs(i, j);
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      }
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    }
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  }
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  // If land is found, increase the count and walk around land(adjacent indexes) to mark them as visited.
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  for (let i = 1; i <= rows - 1; i++) {
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    for (let j = 1; j <= cols - 1; j++) {
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      if (grid[i][j] === 0) {
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        islandCount++;
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        dfs(i, j);
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      }
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    }
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  }
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  // To walk around land and mark it as visited
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  function dfs(x, y) {
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    if (x < 0 || y < 0 || x >= rows || y >= cols) return;
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    if (grid[x][y] !== 0) return;
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    grid[x][y] = 2;
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    dfs(x + 1, y);
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    dfs(x, y + 1);
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    dfs(x - 1, y);
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    dfs(x, y - 1);
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  }
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  return islandCount;
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};