Data Structures: Remove Elements from a Linked List by Index

Data Structures/linkedListClassRemoveByIndex.js

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+// https://www.freecodecamp.org/learn/coding-interview-prep/data-structures/remove-elements-from-a-linked-list-by-index
+
+function LinkedList() {
+  var length = 0;
+  var head = null;
+
+  var Node = function (element) {
+    this.element = element;
+    this.next = null;
+  };
+
+  this.size = function () {
+    return length;
+  };
+
+  this.head = function () {
+    return head;
+  };
+
+  this.add = function (element) {
+    var node = new Node(element);
+    if (head === null) {
+      head = node;
+    } else {
+      var currentNode = head;
+
+      while (currentNode.next) {
+        currentNode = currentNode.next;
+      }
+
+      currentNode.next = node;
+    }
+
+    length++;
+  };
+
+  // Only change code below this line
+  this.removeAt = (index) => {
+    if (index < 0 || index >= length || head === null) {
+      return null;
+    }
+    let i = 0;
+    let previousNode = null;
+    let currentNode = head;
+    while (i < index && currentNode !== null) {
+      i++;
+      previousNode = currentNode;
+      currentNode = currentNode.next;
+    }
+    if (currentNode === null) {
+      return null;
+    }
+    if (previousNode === null) {
+      head = currentNode.next;
+    } else {
+      previousNode.next = currentNode.next;
+    }
+    length--;
+    return currentNode.element;
+  };
+  // Only change code above this line
+}