Easy JS Solution
\nvar middleNode = function(head) {\n    let slow = head, fast = head;\n    while (fast !== null) {\n        fast = fast.next;\n        if (fast == null) break;
```\nvar middleNode = function(head) {\n    let slow = head, fast = head;\n    while (fast !== null) {\n        fast = fast.next;\n        if (fast == null) break;\n        else fast = fast.next;\n        \n        slow = slow.next;\n    }\n    return slow;\n    // Time Complexity: O(n)\n    // Space Complexity: O(1)\n};\n```
['JavaScript']