add ReverseLinkedList.js

CONTRIBUTING.md

@@ -12,4 +12,5 @@
 - ShivayeModi
 - Vishvesh Trivedi
 - Fahri Gunadi
-- ekoyanu99
+- ekoyanu99
+- Bagus

src/Javascript/ReverseLinkedList.js

@@ -0,0 +1,39 @@
+class ListNode {
+  constructor(val, next = null) {
+
+    this.val = val;
+    this.next = next;
+  }
+}
+
+const linkedList = [5, 4, 3, 2, 1].reduce((acc, val) => new ListNode(val, acc), null);
+
+
+const printList = (head) => {
+  if(!head) {
+    return;
+  }
+
+  console.log(head.val);
+  printList(head.next);
+}
+
+// --------- solution -----------
+
+var reverseList = function(head) {
+  let prev = null;
+  let current = head;
+
+  while(current) {
+    let nextTemp = current.next;
+    current.next = prev;
+    prev = current;
+    current = nextTemp;
+  }
+
+  return prev;
+};
+
+printList(linkedList);
+console.log('after reverse')
+printList(reverseList(linkedList))