Spiral Matrix
<p>Given an <code>m x n</code> <code>matrix</code>, return <em>all elements of the</em> <code>matrix</code> <em>in spiral order</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://fastly.jsdelivr.net/gh/doocs/leetcode@main/solution/0000-0099/0054.Spiral%20Matrix/images/spiral1.jpg" style="width: 242px; height: 242px;" />
<pre>
<strong>Input:</strong> matrix = [[1,2,3],[4,5,6],[7,8,9]]
<strong>Output:</strong> [1,2,3,6,9,8,7,4,5]
</pre>

<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://fastly.jsdelivr.net/gh/doocs/leetcode@main/solution/0000-0099/0054.Spiral%20Matrix/images/spiral.jpg" style="width: 322px; height: 242px;" />
<pre>
<strong>Input:</strong> matrix = [[1,2,3,4],[5,6,7,8],[9,10,11,12]]
<strong>Output:</strong> [1,2,3,4,8,12,11,10,9,5,6,7]
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>m == matrix.length</code></li>
	<li><code>n == matrix[i].length</code></li>
	<li><code>1 &lt;= m, n &lt;= 10</code></li>
	<li><code>-100 &lt;= matrix[i][j] &lt;= 100</code></li>
</ul>
Array; Matrix; Simulation
/**
 * @param {number[][]} matrix
 * @return {number[]}
 */
var spiralOrder = function (matrix) {
    const m = matrix.length;
    const n = matrix[0].length;
    const ans = [];
    const vis = Array.from({ length: m }, () => Array(n).fill(false));
    const dirs = [0, 1, 0, -1, 0];
    for (let h = m * n, i = 0, j = 0, k = 0; h > 0; --h) {
        ans.push(matrix[i][j]);
        vis[i][j] = true;
        const x = i + dirs[k];
        const y = j + dirs[k + 1];
        if (x < 0 || x >= m || y < 0 || y >= n || vis[x][y]) {
            k = (k + 1) % 4;
        }
        i += dirs[k];
        j += dirs[k + 1];
    }
    return ans;
};
