[못품/릿코드/javascript] 876.Middle of the Linked List

var middleNode = function(head) {
    let p1 = head;
    let p2 = head;
    while(p2!==null&&p2.next!==null){
        p1 = p1.next;
        p2 = p2.next.next;
    }
    return p1;
};