16     removeLink(node) {  argument
17         if (node.prev) node.prev.next = node.next;else this.head = node.next;
18         if (node.next) node.next.prev = node.prev;else this.tail = node.prev;
20         node.prev = node.next = null;
22         return node;
30     insertAfter(node, newNode) {  argument
31         newNode.prev = node;
32         newNode.next = node.next;
33         if (node.next) node.next.prev = newNode;else this.tail = newNode;
34         node.next = newNode;
38     insertBefore(node, newNode) {  argument
39         newNode.prev = node.prev;
40         newNode.next = node;
41         if (node.prev) node.prev.next = newNode;else this.head = newNode;
42         node.prev = newNode;
46     unshift(node) {  argument
47         if (this.head) this.insertBefore(this.head, node);else setInitial(this, node);
50     push(node) {  argument
51         if (this.tail) this.insertAfter(this.tail, node);else setInitial(this, node);
88 function setInitial(dll, node) {  argument
90     dll.head = dll.tail = node;