added unit testing, and started implementing unit tests...phew

node_modules/async/internal/DoublyLinkedList.js

@@ -0,0 +1,88 @@
+"use strict";
+
+Object.defineProperty(exports, "__esModule", {
+    value: true
+});
+exports.default = DLL;
+// Simple doubly linked list (https://en.wikipedia.org/wiki/Doubly_linked_list) implementation
+// used for queues. This implementation assumes that the node provided by the user can be modified
+// to adjust the next and last properties. We implement only the minimal functionality
+// for queue support.
+function DLL() {
+    this.head = this.tail = null;
+    this.length = 0;
+}
+
+function setInitial(dll, node) {
+    dll.length = 1;
+    dll.head = dll.tail = node;
+}
+
+DLL.prototype.removeLink = function (node) {
+    if (node.prev) node.prev.next = node.next;else this.head = node.next;
+    if (node.next) node.next.prev = node.prev;else this.tail = node.prev;
+
+    node.prev = node.next = null;
+    this.length -= 1;
+    return node;
+};
+
+DLL.prototype.empty = function () {
+    while (this.head) this.shift();
+    return this;
+};
+
+DLL.prototype.insertAfter = function (node, newNode) {
+    newNode.prev = node;
+    newNode.next = node.next;
+    if (node.next) node.next.prev = newNode;else this.tail = newNode;
+    node.next = newNode;
+    this.length += 1;
+};
+
+DLL.prototype.insertBefore = function (node, newNode) {
+    newNode.prev = node.prev;
+    newNode.next = node;
+    if (node.prev) node.prev.next = newNode;else this.head = newNode;
+    node.prev = newNode;
+    this.length += 1;
+};
+
+DLL.prototype.unshift = function (node) {
+    if (this.head) this.insertBefore(this.head, node);else setInitial(this, node);
+};
+
+DLL.prototype.push = function (node) {
+    if (this.tail) this.insertAfter(this.tail, node);else setInitial(this, node);
+};
+
+DLL.prototype.shift = function () {
+    return this.head && this.removeLink(this.head);
+};
+
+DLL.prototype.pop = function () {
+    return this.tail && this.removeLink(this.tail);
+};
+
+DLL.prototype.toArray = function () {
+    var arr = Array(this.length);
+    var curr = this.head;
+    for (var idx = 0; idx < this.length; idx++) {
+        arr[idx] = curr.data;
+        curr = curr.next;
+    }
+    return arr;
+};
+
+DLL.prototype.remove = function (testFn) {
+    var curr = this.head;
+    while (!!curr) {
+        var next = curr.next;
+        if (testFn(curr)) {
+            this.removeLink(curr);
+        }
+        curr = next;
+    }
+    return this;
+};
+module.exports = exports["default"];