Data Structures: Create a Doubly Linked List

Data Structures/doublyLinkedList.js

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+// https://www.freecodecamp.org/learn/coding-interview-prep/data-structures/create-a-doubly-linked-list
+
+var Node = function (data, prev) {
+  this.data = data;
+  this.prev = prev;
+  this.next = null;
+};
+var DoublyLinkedList = function () {
+  this.head = null;
+  this.tail = null;
+  // Only change code below this line
+  this.add = (element) => {
+    const node = new Node(element, this.tail);
+    if (this.head === null) {
+      this.head = node;
+      this.tail = node;
+    } else {
+      this.tail.next = node;
+      this.tail = node;
+    }
+  };
+
+  this.remove = (element) => {
+    let prevNode = null;
+    let currentNode = this.head;
+    while (currentNode !== null && currentNode.data !== element) {
+      prevNode = currentNode;
+      currentNode = currentNode.next;
+    }
+    if (currentNode === null || currentNode.data !== element) {
+      return;
+    }
+    if (prevNode === null) {
+      this.head = currentNode.next;
+    } else {
+      prevNode.next = currentNode.next;
+    }
+    if (currentNode.next === null) {
+      this.tail = prevNode;
+    } else {
+      const nextNode = currentNode.next;
+      nextNode.prev = prevNode;
+    }
+    return currentNode.element;
+  };
+  // Only change code above this line
+};