Update README.md

Author: yanglbme

solution/0900-0999/0959.Regions Cut By Slashes/README.md

@@ -279,6 +279,62 @@ func regionsBySlashes(grid []string) int {
 }
 ```
 
+#### JavaScript
+
+```js
+/**
+ * @param {string[]} grid
+ * @return {number}
+ */
+
+function regionsBySlashes(grid) {
+    const find = x => {
+        if (p[x] !== x) {
+            p[x] = find(p[x]);
+        }
+        return p[x];
+    };
+
+    const union = (a, b) => {
+        const pa = find(a);
+        const pb = find(b);
+        if (pa !== pb) {
+            p[pa] = pb;
+            size--;
+        }
+    };
+
+    const n = grid.length;
+    let size = n * n * 4;
+    const p = Array.from({ length: size }, (_, i) => i);
+
+    for (let i = 0; i < n; i++) {
+        for (let j = 0; j < n; j++) {
+            const k = i * n + j;
+            if (i < n - 1) {
+                union(4 * k + 2, (k + n) * 4);
+            }
+            if (j < n - 1) {
+                union(4 * k + 1, (k + 1) * 4 + 3);
+            }
+            if (grid[i][j] === '/') {
+                union(4 * k, 4 * k + 3);
+                union(4 * k + 1, 4 * k + 2);
+            } else if (grid[i][j] === '\\') {
+                union(4 * k, 4 * k + 1);
+                union(4 * k + 2, 4 * k + 3);
+            } else {
+                union(4 * k, 4 * k + 1);
+                union(4 * k + 1, 4 * k + 2);
+                union(4 * k + 2, 4 * k + 3);
+            }
+        }
+    }
+
+    return size;
+}
+```
+
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 <!-- solution:end -->