diff --git a/.github/workflows/nodejs.yml b/.github/workflows/nodejs.yml
index 361d1abadd..39b9ee5447 100644
--- a/.github/workflows/nodejs.yml
+++ b/.github/workflows/nodejs.yml
@@ -15,12 +15,10 @@ jobs:
     - name: npm install, build, and test
       run: |
         npm install doctest standard --save-dev
-        npx doctest **/*.js || true  # TODO: error: Line 1: Unexpected token >>
+        npx doctest **/*.js || true  # TODO: Add all doctests
         npx standard
         npm ci
         npm run build --if-present
-        # TODO: Remove the next line when #539 is fixed.
-        rm  Linear-Algebra/test/test.js String/LevenshteinDistance.test.js
         npm test
       env:
         CI: true
diff --git a/Conversions/DecimalToBinary.js b/Conversions/DecimalToBinary.js
index a179dbaf2e..9c8337b687 100644
--- a/Conversions/DecimalToBinary.js
+++ b/Conversions/DecimalToBinary.js
@@ -1,5 +1,5 @@
 function decimalToBinary (num) {
-  var bin = []
+  const bin = []
   while (num > 0) {
     bin.unshift(num % 2)
     num >>= 1 // basically /= 2 without remainder if any
diff --git a/Conversions/HexToRGB.js b/Conversions/HexToRGB.js
index 5ee820b817..56e31abd7d 100644
--- a/Conversions/HexToRGB.js
+++ b/Conversions/HexToRGB.js
@@ -1,12 +1,12 @@
 function hexStringToRGB (hexString) {
-  var r = hexString.substring(0, 2)
-  var g = hexString.substring(2, 4)
-  var b = hexString.substring(4, 6)
+  let r = hexString.substring(0, 2)
+  let g = hexString.substring(2, 4)
+  let b = hexString.substring(4, 6)
 
   r = parseInt(r, 16)
   g = parseInt(g, 16)
   b = parseInt(b, 16)
-  var obj = { r, g, b }
+  const obj = { r, g, b }
 
   return obj
 }
diff --git a/Conversions/RomanToDecimal.js b/Conversions/RomanToDecimal.js
index 24f7b0fe61..6de4afa0c3 100644
--- a/Conversions/RomanToDecimal.js
+++ b/Conversions/RomanToDecimal.js
@@ -1,4 +1,4 @@
-var values = {
+const values = {
   I: 1,
   V: 5,
   X: 10,
diff --git a/Data-Structures/Linked-List/SinglyLinkList.js b/Data-Structures/Linked-List/SinglyLinkList.js
index fbfdacf22c..f718962bc2 100644
--- a/Data-Structures/Linked-List/SinglyLinkList.js
+++ b/Data-Structures/Linked-List/SinglyLinkList.js
@@ -10,7 +10,7 @@
 
 // class LinkedList and constructor
 // Creates a LinkedList
-var LinkedList = (function () {
+const LinkedList = (function () {
   function LinkedList () {
     // Length of linklist and head is null at start
     this.length = 0
@@ -19,7 +19,7 @@ var LinkedList = (function () {
 
   // class node (constructor)
   // Creating Node with element's value
-  var Node = (function () {
+  const Node = (function () {
     function Node (element) {
       this.element = element
       this.next = null
@@ -39,12 +39,12 @@ var LinkedList = (function () {
 
   // Creates a node and adds it to linklist
   LinkedList.prototype.add = function (element) {
-    var node = new Node(element)
+    const node = new Node(element)
     // Check if its the first element
     if (this.head === null) {
       this.head = node
     } else {
-      var currentNode = this.head
+      let currentNode = this.head
 
       // Loop till there is node present in the list
       while (currentNode.next) {
@@ -60,8 +60,8 @@ var LinkedList = (function () {
 
   // Removes the node with the value as param
   LinkedList.prototype.remove = function (element) {
-    var currentNode = this.head
-    var previousNode
+    let currentNode = this.head
+    let previousNode
 
     // Check if the head node is the element to remove
     if (currentNode.element === element) {
@@ -88,8 +88,8 @@ var LinkedList = (function () {
 
   // Returns the index of the element passed as param otherwise -1
   LinkedList.prototype.indexOf = function (element) {
-    var currentNode = this.head
-    var index = -1
+    let currentNode = this.head
+    let index = -1
 
     while (currentNode) {
       index++
@@ -106,8 +106,8 @@ var LinkedList = (function () {
 
   // Returns the element at an index
   LinkedList.prototype.elementAt = function (index) {
-    var currentNode = this.head
-    var count = 0
+    let currentNode = this.head
+    let count = 0
     while (count < index) {
       count++
       currentNode = currentNode.next
@@ -118,11 +118,11 @@ var LinkedList = (function () {
   // Adds the element at specified index
   LinkedList.prototype.addAt = function (index, element) {
     index--
-    var node = new Node(element)
+    const node = new Node(element)
 
-    var currentNode = this.head
-    var previousNode
-    var currentIndex = 0
+    let currentNode = this.head
+    let previousNode
+    let currentIndex = 0
 
     // Check if index is out of bounds of list
     if (index > this.length) {
@@ -153,9 +153,9 @@ var LinkedList = (function () {
   // Removes the node at specified index
   LinkedList.prototype.removeAt = function (index) {
     index--
-    var currentNode = this.head
-    var previousNode
-    var currentIndex = 0
+    let currentNode = this.head
+    let previousNode
+    let currentIndex = 0
 
     // Check if index is present in list
     if (index < 0 || index >= this.length) {
@@ -181,8 +181,8 @@ var LinkedList = (function () {
 
   // Function to view the LinkedList
   LinkedList.prototype.view = function () {
-    var currentNode = this.head
-    var count = 0
+    let currentNode = this.head
+    let count = 0
     while (count < this.length) {
       count++
       console.log(currentNode.element)
@@ -195,7 +195,7 @@ var LinkedList = (function () {
 }())
 
 // Implementation of LinkedList
-var linklist = new LinkedList()
+const linklist = new LinkedList()
 linklist.add(2)
 linklist.add(5)
 linklist.add(8)
diff --git a/Data-Structures/Stack/Stack.js b/Data-Structures/Stack/Stack.js
index f95b940599..e6b99b40b0 100644
--- a/Data-Structures/Stack/Stack.js
+++ b/Data-Structures/Stack/Stack.js
@@ -8,7 +8,7 @@
 // Functions: push, pop, peek, view, length
 
 // Creates a stack constructor
-var Stack = (function () {
+const Stack = (function () {
   function Stack () {
     // The top of the Stack
     this.top = 0
@@ -29,7 +29,7 @@ var Stack = (function () {
     }
 
     this.top--
-    var result = this.stack[this.top]
+    const result = this.stack[this.top]
     this.stack = this.stack.splice(0, this.top)
     return result
   }
@@ -46,14 +46,14 @@ var Stack = (function () {
 
   // To see all the elements in the stack
   Stack.prototype.view = function () {
-    for (var i = 0; i < this.top; i++) { console.log(this.stack[i]) }
+    for (let i = 0; i < this.top; i++) { console.log(this.stack[i]) }
   }
 
   return Stack
 }())
 
 // Implementation
-var myStack = new Stack()
+const myStack = new Stack()
 
 myStack.push(1)
 myStack.push(5)
diff --git a/Data-Structures/Tree/BinarySearchTree.js b/Data-Structures/Tree/BinarySearchTree.js
index 943332d54c..a0965cd941 100644
--- a/Data-Structures/Tree/BinarySearchTree.js
+++ b/Data-Structures/Tree/BinarySearchTree.js
@@ -11,7 +11,7 @@
 */
 
 // class Node
-var Node = (function () {
+const Node = (function () {
   // Node in the tree
   function Node (val) {
     this.value = val
@@ -67,7 +67,7 @@ var Node = (function () {
 }())
 
 // class Tree
-var Tree = (function () {
+const Tree = (function () {
   function Tree () {
     // Just store the root
     this.root = null
@@ -103,7 +103,7 @@ var Tree = (function () {
 }())
 
 // Implementation of BST
-var bst = new Tree()
+const bst = new Tree()
 bst.addValue(6)
 bst.addValue(3)
 bst.addValue(9)
diff --git a/Data-Structures/Tree/Trie.js b/Data-Structures/Tree/Trie.js
index 0103662862..1e00daf538 100644
--- a/Data-Structures/Tree/Trie.js
+++ b/Data-Structures/Tree/Trie.js
@@ -1,4 +1,4 @@
-var TrieNode = function TrieNode (key, parent) {
+const TrieNode = function TrieNode (key, parent) {
   this.key = key
   this.count = 0
   this.children = Object.create(null)
@@ -20,7 +20,7 @@ Trie.findAllWords = function (root, word, output) {
   if (root.count > 0) {
     if (typeof output === 'object') { output.push({ word: word, count: root.count }) }
   }
-  var key
+  let key
   for (key in root.children) {
     word += key
     this.findAllWords(root.children[key], word, output)
@@ -34,9 +34,9 @@ Trie.prototype.insert = function (word) {
     this.root.count += 1
     return
   }
-  var node = this.root
-  var len = word.length
-  var i
+  let node = this.root
+  const len = word.length
+  let i
   for (i = 0; i < len; i++) {
     if (node.children[word.charAt(i)] === undefined) { node.children[word.charAt(i)] = new TrieNode(word.charAt(i), node) }
     node = node.children[word.charAt(i)]
@@ -46,9 +46,9 @@ Trie.prototype.insert = function (word) {
 
 Trie.prototype.findPrefix = function (word) {
   if (typeof word !== 'string') return null
-  var node = this.root
-  var len = word.length
-  var i
+  let node = this.root
+  const len = word.length
+  let i
   // After end of this loop node will be at desired prefix
   for (i = 0; i < len; i++) {
     if (node.children[word.charAt(i)] === undefined) return null // No such prefix exists
@@ -69,9 +69,9 @@ Trie.prototype.remove = function (word, count) {
     return
   }
 
-  var child = this.root
-  var len = word.length
-  var i, key
+  let child = this.root
+  const len = word.length
+  let i, key
   // child: node which is to be deleted
   for (i = 0; i < len; i++) {
     key = word.charAt(i)
@@ -93,9 +93,9 @@ Trie.prototype.remove = function (word, count) {
 }
 
 Trie.prototype.findAllWords = function (prefix) {
-  var output = []
+  const output = []
   // find the node with provided prefix
-  var node = this.findPrefix(prefix)
+  const node = this.findPrefix(prefix)
   // No such prefix exists
   if (node === null) return output
   Trie.findAllWords(node, prefix, output)
@@ -104,7 +104,7 @@ Trie.prototype.findAllWords = function (prefix) {
 
 Trie.prototype.contains = function (word) {
   // find the node with given prefix
-  var node = this.findPrefix(word)
+  const node = this.findPrefix(word)
   // No such word exists
   if (node === null || node.count === 0) return false
   return true
@@ -112,7 +112,7 @@ Trie.prototype.contains = function (word) {
 
 Trie.prototype.findOccurences = function (word) {
   // find the node with given prefix
-  var node = this.findPrefix(word)
+  const node = this.findPrefix(word)
   // No such word exists
   if (node === null) return 0
   return node.count
@@ -120,7 +120,7 @@ Trie.prototype.findOccurences = function (word) {
 
 // To test
 (function demo () {
-  var x = new Trie()
+  const x = new Trie()
   x.insert('sheldon')
   x.insert('hello')
   x.insert('anyword')
diff --git a/Dynamic-Programming/ZeroOneKnapsack.js b/Dynamic-Programming/ZeroOneKnapsack.js
index 0274fdefdb..f3c47135fc 100644
--- a/Dynamic-Programming/ZeroOneKnapsack.js
+++ b/Dynamic-Programming/ZeroOneKnapsack.js
@@ -50,10 +50,9 @@ const main = () => {
       arr.push(input[j])
       j++
     }
-    const newArr = []
-    arr.map(e => {
-      newArr.push(e.trim().split(' ').map(Number))
-    })
+    const newArr = arr.map(e =>
+      e.trim().split(' ').map(Number)
+    )
     const cache = []
     for (let i = 0; i <= currlen; i++) {
       const temp = []
diff --git a/Linear-Algebra/src/la_lib.js b/Linear-Algebra/src/la_lib.js
index be9f507def..41f99a3078 100644
--- a/Linear-Algebra/src/la_lib.js
+++ b/Linear-Algebra/src/la_lib.js
@@ -5,13 +5,13 @@
     The namespace LinearAlgebra contains useful classes and functions for dealing with
     linear algebra under JavaScript.
 */
-var LinearAlgebra;
+let LinearAlgebra;
 (function (LinearAlgebra) {
   /*
         class: Vector
         This class represents a vector of arbitrary size and operations on it.
     */
-  var Vector = /** @class */ (function () {
+  const Vector = /** @class */ (function () {
     // constructor
     function Vector (N, comps) {
       if (comps === undefined) {
@@ -19,7 +19,7 @@ var LinearAlgebra;
       }
       this.components = new Array(N)
       if (comps.length === 0) {
-        for (var i = 0; i < N; i++) {
+        for (let i = 0; i < N; i++) {
           this.components[i] = 0.0
         }
       } else {
@@ -37,8 +37,8 @@ var LinearAlgebra;
     }
     // computes the eulidean length.
     Vector.prototype.eulideanLength = function () {
-      var sum = 0
-      for (var i = 0; i < this.components.length; i++) {
+      let sum = 0
+      for (let i = 0; i < this.components.length; i++) {
         sum += this.components[i] * this.components[i]
       }
       return Math.sqrt(sum)
@@ -59,9 +59,9 @@ var LinearAlgebra;
     // vector addition
     Vector.prototype.add = function (other) {
       if (this.size() === other.size()) {
-        var SIZE = this.size()
-        var ans = new Vector(SIZE)
-        for (var i = 0; i < SIZE; i++) {
+        const SIZE = this.size()
+        const ans = new Vector(SIZE)
+        for (let i = 0; i < SIZE; i++) {
           ans.changeComponent(i, (this.components[i] + other.component(i)))
         }
         return ans
@@ -72,9 +72,9 @@ var LinearAlgebra;
     // vector subtraction
     Vector.prototype.sub = function (other) {
       if (this.size() === other.size()) {
-        var SIZE = this.size()
-        var ans = new Vector(SIZE)
-        for (var i = 0; i < SIZE; i++) {
+        const SIZE = this.size()
+        const ans = new Vector(SIZE)
+        for (let i = 0; i < SIZE; i++) {
           ans.changeComponent(i, (this.components[i] - other.component(i)))
         }
         return ans
@@ -84,10 +84,10 @@ var LinearAlgebra;
     }
     // dot-product
     Vector.prototype.dot = function (other) {
-      var sum = 0
+      let sum = 0
       if (other.size() === this.size()) {
-        var SIZE = other.size()
-        for (var i = 0; i < SIZE; i++) {
+        const SIZE = other.size()
+        for (let i = 0; i < SIZE; i++) {
           sum += this.components[i] * other.component(i)
         }
         return sum
@@ -97,18 +97,18 @@ var LinearAlgebra;
     }
     // scalar multiplication
     Vector.prototype.scalar = function (s) {
-      var SIZE = this.size()
-      var ans = new Vector(SIZE)
-      for (var i = 0; i < SIZE; i++) {
+      const SIZE = this.size()
+      const ans = new Vector(SIZE)
+      for (let i = 0; i < SIZE; i++) {
         ans.changeComponent(i, (this.components[i] * s))
       }
       return ans
     }
     // returns a string representation of this vector.
     Vector.prototype.toString = function () {
-      var ans = '('
-      var SIZE = this.components.length
-      for (var i = 0; i < SIZE; i++) {
+      let ans = '('
+      const SIZE = this.components.length
+      for (let i = 0; i < SIZE; i++) {
         if (i < SIZE - 1) {
           ans += this.components[i] + ','
         } else {
@@ -121,7 +121,7 @@ var LinearAlgebra;
     // the One is on position 'pos'
     Vector.prototype.createUnitBasis = function (pos) {
       if (pos >= 0 && pos < this.components.length) {
-        for (var i = 0; i < this.components.length; i++) {
+        for (let i = 0; i < this.components.length; i++) {
           if (i === pos) {
             this.components[i] = 1.0
           } else {
@@ -135,20 +135,20 @@ var LinearAlgebra;
     }
     // normalizes this vector and returns it.
     Vector.prototype.norm = function () {
-      var SIZE = this.size()
-      var quotient = 1.0 / this.eulideanLength()
-      for (var i = 0; i < SIZE; i++) {
+      const SIZE = this.size()
+      const quotient = 1.0 / this.eulideanLength()
+      for (let i = 0; i < SIZE; i++) {
         this.components[i] = this.components[i] * quotient
       }
       return this
     }
     // returns true if the vectors are equal otherwise false.
     Vector.prototype.equal = function (other) {
-      var ans = true
-      var SIZE = this.size()
-      var EPSILON = 0.001
+      let ans = true
+      const SIZE = this.size()
+      const EPSILON = 0.001
       if (SIZE === other.size()) {
-        for (var i = 0; i < SIZE; i++) {
+        for (let i = 0; i < SIZE; i++) {
           if (Math.abs(this.components[i] - other.component(i)) > EPSILON) {
             ans = false
           }
@@ -164,8 +164,8 @@ var LinearAlgebra;
   // -------------- global functions ---------------------------------
   // returns a unit basis vector of size N with a One on position 'pos'
   function unitBasisVector (N, pos) {
-    var ans = new Vector(N)
-    for (var i = 0; i < N; i++) {
+    const ans = new Vector(N)
+    for (let i = 0; i < N; i++) {
       if (i === pos) {
         ans.changeComponent(i, 1.0)
       } else {
@@ -177,8 +177,8 @@ var LinearAlgebra;
   LinearAlgebra.unitBasisVector = unitBasisVector
   // returns a random vector with integer components (between 'a' and 'b') of size N.
   function randomVectorInt (N, a, b) {
-    var ans = new Vector(N)
-    for (var i = 0; i < N; i++) {
+    const ans = new Vector(N)
+    for (let i = 0; i < N; i++) {
       ans.changeComponent(i, (Math.floor((Math.random() * b) + a)))
     }
     return ans
@@ -186,8 +186,8 @@ var LinearAlgebra;
   LinearAlgebra.randomVectorInt = randomVectorInt
   // returns a random vector with floating point components (between 'a' and 'b') of size N.
   function randomVectorFloat (N, a, b) {
-    var ans = new Vector(N)
-    for (var i = 0; i < N; i++) {
+    const ans = new Vector(N)
+    for (let i = 0; i < N; i++) {
       ans.changeComponent(i, ((Math.random() * b) + a))
     }
     return ans
@@ -198,7 +198,7 @@ var LinearAlgebra;
         class: Matrix
         This class represents a matrix of arbitrary size and operations on it.
     */
-  var Matrix = /** @class */ (function () {
+  const Matrix = /** @class */ (function () {
     // constructor for zero-matrix or fix number matrix.
     function Matrix (row, col, comps) {
       if (comps === undefined) {
@@ -206,9 +206,9 @@ var LinearAlgebra;
       }
       if (comps.length === 0) {
         this.matrix = []
-        var rowVector = []
-        for (var i = 0; i < row; i++) {
-          for (var j = 0; j < col; j++) {
+        let rowVector = []
+        for (let i = 0; i < row; i++) {
+          for (let j = 0; j < col; j++) {
             rowVector[j] = 0
           }
           this.matrix[i] = rowVector
@@ -238,10 +238,10 @@ var LinearAlgebra;
     }
     // returns a string representation of this matrix.
     Matrix.prototype.toString = function () {
-      var ans = ''
-      for (var i = 0; i < this.rows; i++) {
+      let ans = ''
+      for (let i = 0; i < this.rows; i++) {
         ans += '|'
-        for (var j = 0; j < this.cols; j++) {
+        for (let j = 0; j < this.cols; j++) {
           if (j < this.cols - 1) {
             ans += this.matrix[i][j] + ','
           } else {
@@ -257,7 +257,7 @@ var LinearAlgebra;
     }
     // returns the dimension rows x cols as number array
     Matrix.prototype.dimension = function () {
-      var ans = []
+      const ans = []
       ans[0] = this.rows
       ans[1] = this.cols
       return ans
@@ -266,9 +266,9 @@ var LinearAlgebra;
     Matrix.prototype.add = function (other) {
       if (this.rows === other.dimension()[0] &&
         this.cols === other.dimension()[1]) {
-        var ans = new Matrix(this.rows, this.cols)
-        for (var i = 0; i < this.rows; i++) {
-          for (var j = 0; j < this.cols; j++) {
+        const ans = new Matrix(this.rows, this.cols)
+        for (let i = 0; i < this.rows; i++) {
+          for (let j = 0; j < this.cols; j++) {
             ans.changeComponent(i, j, (this.matrix[i][j] + other.component(i, j)))
           }
         }
@@ -279,12 +279,12 @@ var LinearAlgebra;
     }
     // returns true if the matrices are equal, otherwise false.
     Matrix.prototype.equal = function (other) {
-      var ans = true
-      var EPSILON = 0.001
+      let ans = true
+      const EPSILON = 0.001
       if (this.rows === other.dimension()[0] &&
         this.cols === other.dimension()[1]) {
-        for (var i = 0; i < this.rows; i++) {
-          for (var j = 0; j < this.cols; j++) {
+        for (let i = 0; i < this.rows; i++) {
+          for (let j = 0; j < this.cols; j++) {
             if (Math.abs(this.matrix[i][j] - other.component(i, j)) > EPSILON) {
               ans = false
             }
@@ -297,9 +297,9 @@ var LinearAlgebra;
     }
     // matrix-scalar multiplication
     Matrix.prototype.scalar = function (c) {
-      var ans = new Matrix(this.rows, this.cols)
-      for (var i = 0; i < this.rows; i++) {
-        for (var j = 0; j < this.cols; j++) {
+      const ans = new Matrix(this.rows, this.cols)
+      for (let i = 0; i < this.rows; i++) {
+        for (let j = 0; j < this.cols; j++) {
           ans.changeComponent(i, j, (this.matrix[i][j] * c))
         }
       }
@@ -309,3 +309,5 @@ var LinearAlgebra;
   }()) // end of class Matrix
   LinearAlgebra.Matrix = Matrix
 })(LinearAlgebra || (LinearAlgebra = {})) // end of namespace LinearAlgebra
+
+export { LinearAlgebra }
diff --git a/Linear-Algebra/test/test.js b/Linear-Algebra/test/test.js
index 5f1892db89..1deb0f8b29 100644
--- a/Linear-Algebra/test/test.js
+++ b/Linear-Algebra/test/test.js
@@ -7,11 +7,12 @@
 */
 /* eslint-disable */
 
+import { LinearAlgebra } from "../src/la_lib"
+
 var assert = require('assert')
 var fs = require('fs')
 
 // file is included here
-eval(fs.readFileSync('src/la_lib.js') + '')
 // Tests goes here
 
 // creating some vectors
diff --git a/Maths/Fibonacci.js b/Maths/Fibonacci.js
index 6a204a9549..c1b153f24d 100644
--- a/Maths/Fibonacci.js
+++ b/Maths/Fibonacci.js
@@ -63,7 +63,7 @@ const FibonacciDpWithoutRecursion = (number) => {
   const table = []
   table.push(1)
   table.push(1)
-  for (var i = 2; i < number; ++i) {
+  for (let i = 2; i < number; ++i) {
     table.push(table[i - 1] + table[i - 2])
   }
   return table
diff --git a/Maths/Polynomial.js b/Maths/Polynomial.js
index 41ec340ee7..5df31fdc00 100644
--- a/Maths/Polynomial.js
+++ b/Maths/Polynomial.js
@@ -32,11 +32,9 @@ class Polynomial {
           return `(${coefficient}x^${exponent})`
         }
       })
-      .filter((x) => {
-        if (x !== '0') {
-          return x
-        }
-      })
+      .filter((x) =>
+        x !== '0'
+      )
       .reverse()
       .join(' + ')
   }
diff --git a/Search/LinearSearch.js b/Search/LinearSearch.js
index 06d9e94a6d..6b4211d40c 100644
--- a/Search/LinearSearch.js
+++ b/Search/LinearSearch.js
@@ -5,7 +5,7 @@
  * have been searched.
  */
 function SearchArray (searchNum, ar) {
-  var position = Search(ar, searchNum)
+  const position = Search(ar, searchNum)
   if (position !== -1) {
     console.log('The element was found at ' + (position + 1))
   } else {
@@ -15,13 +15,13 @@ function SearchArray (searchNum, ar) {
 
 // Search “theArray” for the specified “key” value
 function Search (theArray, key) {
-  for (var n = 0; n < theArray.length; n++) {
+  for (let n = 0; n < theArray.length; n++) {
     if (theArray[n] === key) { return n }
   }
   return -1
 }
 
-var ar = [1, 2, 3, 4, 5, 6, 7, 8, 9]
+const ar = [1, 2, 3, 4, 5, 6, 7, 8, 9]
 SearchArray(3, ar)
 SearchArray(4, ar)
 SearchArray(11, ar)
diff --git a/Sorts/GnomeSort.js b/Sorts/GnomeSort.js
index d8ccd5ce02..64434d5f8d 100644
--- a/Sorts/GnomeSort.js
+++ b/Sorts/GnomeSort.js
@@ -23,7 +23,7 @@ function gnomeSort (items) {
 
 // Implementation of gnomeSort
 
-var ar = [5, 6, 7, 8, 1, 2, 12, 14]
+const ar = [5, 6, 7, 8, 1, 2, 12, 14]
 // Array before Sort
 console.log(ar)
 gnomeSort(ar)
diff --git a/Sorts/HeapSort.js b/Sorts/HeapSort.js
index d7540919e5..1f41c8ab03 100644
--- a/Sorts/HeapSort.js
+++ b/Sorts/HeapSort.js
@@ -50,7 +50,7 @@ function heapSort (items) {
 
 // Implementation of heapSort
 
-var ar = [5, 6, 7, 8, 1, 2, 12, 14]
+const ar = [5, 6, 7, 8, 1, 2, 12, 14]
 // Array before Sort
 console.log(ar)
 heapSort(ar)
diff --git a/Sorts/InsertionSort.js b/Sorts/InsertionSort.js
index 15ec02a600..5812acf819 100644
--- a/Sorts/InsertionSort.js
+++ b/Sorts/InsertionSort.js
@@ -5,11 +5,12 @@
 * the correct position and expand sorted part one element at a time.
 */
 function insertionSort (unsortedList) {
-  var len = unsortedList.length
-  for (var i = 1; i < len; i++) {
-    var tmp = unsortedList[i] // Copy of the current element.
+  const len = unsortedList.length
+  for (let i = 1; i < len; i++) {
+    let j
+    const tmp = unsortedList[i] // Copy of the current element.
     /* Check through the sorted part and compare with the number in tmp. If large, shift the number */
-    for (var j = i - 1; j >= 0 && (unsortedList[j] > tmp); j--) {
+    for (j = i - 1; j >= 0 && (unsortedList[j] > tmp); j--) {
       // Shift the number
       unsortedList[j + 1] = unsortedList[j]
     }
@@ -19,6 +20,6 @@ function insertionSort (unsortedList) {
   }
 }
 
-var arr = [5, 3, 1, 2, 4, 8, 3, 8]
+const arr = [5, 3, 1, 2, 4, 8, 3, 8]
 insertionSort(arr)
 console.log(arr)
diff --git a/Sorts/IntroSort.js b/Sorts/IntroSort.js
index e7ba322c5e..57edb4e8d2 100644
--- a/Sorts/IntroSort.js
+++ b/Sorts/IntroSort.js
@@ -28,12 +28,12 @@ function introsort (array, compare) {
    *  0 if a is equal to b
    *  1 if a greater than b
    */
-  var defaultComparator = function (x, y) {
+  const defaultComparator = function (x, y) {
     if (x === undefined && y === undefined) return 0
     if (x === undefined) return 1
     if (y === undefined) return -1
-    var xString = toString(x)
-    var yString = toString(y)
+    const xString = toString(x)
+    const yString = toString(y)
     if (xString < yString) return -1
     if (xString > yString) return 1
     return 0
@@ -45,7 +45,7 @@ function introsort (array, compare) {
    * @param {Object} obj
    * @returns {String} String representation of given object
    */
-  var toString = function (obj) {
+  const toString = function (obj) {
     if (obj === null) return 'null'
     if (typeof obj === 'boolean' || typeof obj === 'number') {
       return obj.toString()
@@ -75,8 +75,8 @@ function introsort (array, compare) {
    * [IIFE](https://en.wikipedia.org/wiki/Immediately_invoked_function_expression)
    */
   return (function (array, comparator) {
-    var swap = function (index1, index2) {
-      var temp = array[index1]
+    const swap = function (index1, index2) {
+      const temp = array[index1]
       array[index1] = array[index2]
       array[index2] = temp
     }
@@ -85,14 +85,14 @@ function introsort (array, compare) {
      * If the length of array is less than
      * this then we simply perform insertion sort
      */
-    var THRESHOLD = 16
+    const THRESHOLD = 16
     /**
      * @constant TUNEMAXDEPTH
      * Constant usec to increase or decrease value
      * of maxDepth
      */
-    var TUNEMAXDEPTH = 1
-    var len = array.length
+    const TUNEMAXDEPTH = 1
+    const len = array.length
     /**
      * Return if array is only of length 1
      * Array of size 1 is always sorted
@@ -104,7 +104,7 @@ function introsort (array, compare) {
      * Calculate maxDepth = log2(len)
      * Taken from implementation in stdc++
      */
-    var maxDepth = Math.floor(Math.log2(len)) * TUNEMAXDEPTH
+    const maxDepth = Math.floor(Math.log2(len)) * TUNEMAXDEPTH
     /**
      * The very first call to quicksort
      * this initiates sort routine
@@ -133,7 +133,7 @@ function introsort (array, compare) {
         heapSort(start, last)
         return
       }
-      var pivot = (last + start) >> 1
+      let pivot = (last + start) >> 1
       pivot = partition(start, last, pivot)
       quickSort(start, pivot, depth - 1)
       quickSort(pivot + 1, last, depth - 1)
@@ -148,8 +148,8 @@ function introsort (array, compare) {
     function partition (start, last, pivot) {
       swap(start, pivot)
       pivot = start
-      var lo = start
-      var hi = last
+      let lo = start
+      let hi = last
       while (true) {
         lo++
         while (comparator(array[lo], array[pivot]) <= 0 && lo !== last) {
@@ -175,7 +175,7 @@ function introsort (array, compare) {
      * @param {Number} last  one more than last index of array to be sorted
      */
     function insertionSort (start, last) {
-      var i, j
+      let i, j
       for (i = start + 1; i < last; i++) {
         j = i - 1
         while (j >= 0 && comparator(array[j], array[j + 1]) > 0) {
@@ -192,7 +192,7 @@ function introsort (array, compare) {
      * @param {Number} last  one more than last index of array to be sorted
      */
     function heapSort (start, last) {
-      var x = (last + start) >> 1
+      let x = (last + start) >> 1
       while (x - start >= 0) {
         heapify(x, start, last)
         x--
@@ -211,8 +211,8 @@ function introsort (array, compare) {
      * @param {Number} last  one more than last index of segment that cur belongs to
      */
     function heapify (cur, start, last) {
-      var size = last - start
-      var max, lt, rt
+      const size = last - start
+      let max, lt, rt
       cur = cur - start
       while (true) {
         max = cur
@@ -250,9 +250,9 @@ function introsort (array, compare) {
 (function demo () {
   const data = []
   const size = 1000000
-  var i = 0
-  var temp
-  var c = function (a, b) {
+  let i = 0
+  let temp
+  const c = function (a, b) {
     return a - b
   }
   for (i = 0; i < size; i++) {
@@ -260,7 +260,7 @@ function introsort (array, compare) {
     data.push(temp)
   }
   introsort(data, c)
-  var faulty = false
+  let faulty = false
   for (i = 1; i < size; i++) {
     if (data[i] < data[i - 1]) {
       faulty = true
@@ -283,8 +283,8 @@ function introsort (array, compare) {
   const data = []
   const data2 = []
   const size = 1000000
-  var i = 0
-  var temp
+  let i = 0
+  let temp
   for (i = 0; i < size; i++) {
     temp = Math.random() * Number.MAX_SAFE_INTEGER
     data.push(temp)
@@ -292,7 +292,7 @@ function introsort (array, compare) {
   }
   introsort(data)
   data2.sort()
-  var faulty = false
+  let faulty = false
   for (i = 1; i < size; i++) {
     if (data[i] !== data2[i]) {
       faulty = true
diff --git a/Sorts/MergeSort.js b/Sorts/MergeSort.js
index b634704cfb..8e2128f043 100644
--- a/Sorts/MergeSort.js
+++ b/Sorts/MergeSort.js
@@ -35,16 +35,19 @@
 */
 
 function merge (list1, list2) {
-  var results = []
+  const results = []
+  let i = 0
+  let j = 0
 
-  while (list1.length && list2.length) {
-    if (list1[0] <= list2[0]) {
-      results.push(list1.shift())
+  while (i < list1.length && j < list2.length) {
+    if (list1[i] < list2[j]) {
+      results.push(list1[i++])
     } else {
-      results.push(list2.shift())
+      results.push(list2[j++])
     }
   }
-  return results.concat(list1, list2)
+
+  return results.concat(list1.slice(i), list2.slice(j))
 }
 
 /**
@@ -55,15 +58,15 @@ function merge (list1, list2) {
 function mergeSort (list) {
   if (list.length < 2) return list
 
-  var listHalf = Math.floor(list.length / 2)
-  var subList1 = list.slice(0, listHalf)
-  var subList2 = list.slice(listHalf, list.length)
+  const listHalf = Math.floor(list.length / 2)
+  const subList1 = list.slice(0, listHalf)
+  const subList2 = list.slice(listHalf, list.length)
 
   return merge(mergeSort(subList1), mergeSort(subList2))
 }
 
 // Merge Sort Example
-var unsortedArray = [10, 5, 3, 8, 2, 6, 4, 7, 9, 1]
-var sortedArray = mergeSort(unsortedArray)
+const unsortedArray = [10, 5, 3, 8, 2, 6, 4, 7, 9, 1]
+const sortedArray = mergeSort(unsortedArray)
 
 console.log('Before:', unsortedArray, 'After:', sortedArray)
diff --git a/Sorts/QuickSort.js b/Sorts/QuickSort.js
index 933b502caf..204e04b1d8 100644
--- a/Sorts/QuickSort.js
+++ b/Sorts/QuickSort.js
@@ -17,16 +17,16 @@
 */
 
 function quickSort (items) {
-  var length = items.length
+  const length = items.length
 
   if (length <= 1) {
     return items
   }
-  var PIVOT = items[0]
-  var GREATER = []
-  var LESSER = []
+  const PIVOT = items[0]
+  const GREATER = []
+  const LESSER = []
 
-  for (var i = 1; i < length; i++) {
+  for (let i = 1; i < length; i++) {
     if (items[i] > PIVOT) {
       GREATER.push(items[i])
     } else {
@@ -34,7 +34,7 @@ function quickSort (items) {
     }
   }
 
-  var sorted = quickSort(LESSER)
+  let sorted = quickSort(LESSER)
   sorted.push(PIVOT)
   sorted = sorted.concat(quickSort(GREATER))
 
@@ -43,7 +43,7 @@ function quickSort (items) {
 
 // Implementation of quick sort
 
-var ar = [0, 5, 3, 2, 2]
+let ar = [0, 5, 3, 2, 2]
 // Array before Sort
 console.log(ar)
 ar = quickSort(ar)
diff --git a/Sorts/RadixSort.js b/Sorts/RadixSort.js
index b6eb208e99..3696aba961 100644
--- a/Sorts/RadixSort.js
+++ b/Sorts/RadixSort.js
@@ -10,29 +10,29 @@ function radixSort (items, RADIX) {
     RADIX = 10
   }
 
-  var maxLength = false
-  var placement = 1
+  let maxLength = false
+  let placement = 1
 
   while (!maxLength) {
     maxLength = true
-    var buckets = []
+    const buckets = []
 
-    for (var i = 0; i < RADIX; i++) {
+    for (let i = 0; i < RADIX; i++) {
       buckets.push([])
     }
 
-    for (var j = 0; j < items.length; j++) {
-      var tmp = items[j] / placement
+    for (let j = 0; j < items.length; j++) {
+      const tmp = items[j] / placement
       buckets[Math.floor(tmp % RADIX)].push(items[j])
       if (maxLength && tmp > 0) {
         maxLength = false
       }
     }
 
-    var a = 0
-    for (var b = 0; b < RADIX; b++) {
-      var buck = buckets[b]
-      for (var k = 0; k < buck.length; k++) {
+    let a = 0
+    for (let b = 0; b < RADIX; b++) {
+      const buck = buckets[b]
+      for (let k = 0; k < buck.length; k++) {
         items[a] = buck[k]
         a++
       }
@@ -44,7 +44,7 @@ function radixSort (items, RADIX) {
 
 // Implementation of radixSort
 
-var ar = [5, 6, 7, 8, 1, 2, 12, 14]
+const ar = [5, 6, 7, 8, 1, 2, 12, 14]
 // Array before Sort
 console.log(ar)
 radixSort(ar)
diff --git a/Sorts/SelectionSort.test.js b/Sorts/SelectionSort.test.js
index 57ad1e8ecf..090ccc0a5a 100644
--- a/Sorts/SelectionSort.test.js
+++ b/Sorts/SelectionSort.test.js
@@ -2,7 +2,7 @@ import { selectionSort } from './SelectionSort'
 
 describe('selectionSort', () => {
   it('expects to return the array sorted in ascending order', () => {
-    var toSort = [5, 6, 7, 8, 1, 2, 12, 14]
+    const toSort = [5, 6, 7, 8, 1, 2, 12, 14]
     const expected = [1, 2, 5, 6, 7, 8, 12, 14]
 
     expect(selectionSort(toSort)).toEqual(expected)
diff --git a/Sorts/ShellSort.js b/Sorts/ShellSort.js
index 43f29b537a..e32af561c5 100644
--- a/Sorts/ShellSort.js
+++ b/Sorts/ShellSort.js
@@ -4,16 +4,16 @@
  *
  */
 function shellSort (items) {
-  var interval = 1
+  let interval = 1
 
   while (interval < items.length / 3) {
     interval = interval * 3 + 1
   }
 
   while (interval > 0) {
-    for (var outer = interval; outer < items.length; outer++) {
-      var value = items[outer]
-      var inner = outer
+    for (let outer = interval; outer < items.length; outer++) {
+      const value = items[outer]
+      let inner = outer
 
       while (inner > interval - 1 && items[inner - interval] >= value) {
         items[inner] = items[inner - interval]
@@ -28,7 +28,7 @@ function shellSort (items) {
 
 // Implementation of shellSort
 
-var ar = [5, 6, 7, 8, 1, 2, 12, 14]
+const ar = [5, 6, 7, 8, 1, 2, 12, 14]
 // Array before Sort
 console.log(ar)
 shellSort(ar)
diff --git a/Sorts/TopologicalSort.js b/Sorts/TopologicalSort.js
index e784ad0e6b..c9c5dc5e0d 100644
--- a/Sorts/TopologicalSort.js
+++ b/Sorts/TopologicalSort.js
@@ -1,10 +1,10 @@
 
 function TopologicalSorter () {
-  var graph = {}
-  var isVisitedNode
-  var finishTimeCount
-  var finishingTimeList
-  var nextNode
+  const graph = {}
+  let isVisitedNode
+  let finishTimeCount
+  let finishingTimeList
+  let nextNode
 
   this.addOrder = function (nodeA, nodeB) {
     nodeA = String(nodeA)
@@ -18,7 +18,7 @@ function TopologicalSorter () {
     finishTimeCount = 0
     finishingTimeList = []
 
-    for (var node in graph) {
+    for (const node in graph) {
       if (Object.prototype.hasOwnProperty.call(graph, node) && !isVisitedNode[node]) {
         dfsTraverse(node)
       }
@@ -34,7 +34,7 @@ function TopologicalSorter () {
   function dfsTraverse (node) {
     isVisitedNode[node] = true
     if (graph[node]) {
-      for (var i = 0; i < graph[node].length; i++) {
+      for (let i = 0; i < graph[node].length; i++) {
         nextNode = graph[node][i]
         if (isVisitedNode[nextNode]) continue
         dfsTraverse(nextNode)
@@ -49,7 +49,7 @@ function TopologicalSorter () {
 }
 
 /* TEST */
-var topoSorter = new TopologicalSorter()
+const topoSorter = new TopologicalSorter()
 topoSorter.addOrder(5, 2)
 topoSorter.addOrder(5, 0)
 topoSorter.addOrder(4, 0)
diff --git a/Sorts/WiggleSort.js b/Sorts/WiggleSort.js
index fdb2a70db1..4c303c672a 100644
--- a/Sorts/WiggleSort.js
+++ b/Sorts/WiggleSort.js
@@ -18,7 +18,7 @@ Array.prototype.wiggleSort = function () {
 
 // Implementation of wiggle sort
 
-var arr = [3, 5, 2, 1, 6, 4]
+const arr = [3, 5, 2, 1, 6, 4]
 // Array before Wiggle Sort
 console.log(arr) // [3, 5, 2, 1, 6, 4]
 
diff --git a/String/LevenshteinDistance.test.js b/String/LevenshteinDistance.test.js
index 777884c366..e713f6d9e5 100644
--- a/String/LevenshteinDistance.test.js
+++ b/String/LevenshteinDistance.test.js
@@ -1,4 +1,4 @@
-import levenshteinDistance from './LevenshteinDistance'
+import { levenshteinDistance } from './LevenshteinDistance'
 
 describe('levenshteinDistance', () => {
   it('should calculate edit distance between two strings', () => {
@@ -14,13 +14,13 @@ describe('levenshteinDistance', () => {
     // Should just substitute i with o, m with g and insert e at end
     expect(levenshteinDistance('firm', 'forge')).toBe(3)
 
-    // Should just substitute i with s, g with i, h with t and delete f from front
-    expect(levenshteinDistance('fighting', 'sitting')).toBe(4)
+    // Should just substitute f with s, g with t and delete h
+    expect(levenshteinDistance('fighting', 'sitting')).toBe(3)
 
     // Should add 4 letters b, a, s and e at the beginning.
     expect(levenshteinDistance('ball', 'baseball')).toBe(4)
 
-    // Should delete 4 letters b, a, s and e at the beginning.
-    expect(levenshteinDistance('baseball', 'foot')).toBe(4)
+    // Should delete 4 letters b, a, s and e at the beginning and replace the last 4 with f, o, o, t
+    expect(levenshteinDistance('baseball', 'foot')).toBe(8)
   })
 })
diff --git a/String/PermutateString.js b/String/PermutateString.js
index e470d7ac35..8ba4bc8a72 100644
--- a/String/PermutateString.js
+++ b/String/PermutateString.js
@@ -18,7 +18,7 @@ const permutate = (aString) => {
 
 const calculateCurrentCharacterPermutation = (allPermutations, currentCharacter) => {
   const currentPermutations = []
-  allPermutations.map(permutation => {
+  allPermutations.forEach(permutation => {
     let index = 0
     while (index <= permutation.length) {
       const tmp = [...permutation]
diff --git a/Trees/DepthFirstSearch.js b/Trees/DepthFirstSearch.js
index ec8ca7e669..0833d9d1de 100644
--- a/Trees/DepthFirstSearch.js
+++ b/Trees/DepthFirstSearch.js
@@ -25,13 +25,13 @@ function traverseDFS (root) {
 }
 
 function searchDFS (tree, value) {
-  var stack = []
+  const stack = []
 
   stack.push(tree[0])
 
   while (stack.length !== 0) {
     for (let i = 0; i < stack.length; i++) {
-      var node = stack.pop()
+      const node = stack.pop()
 
       if (node.value === value) {
         return node
@@ -47,7 +47,7 @@ function searchDFS (tree, value) {
   return null
 }
 
-var tree = [
+const tree = [
   { value: 6, left: 1, right: 2 },
   { value: 5, left: 3, right: 4 },
   { value: 7, left: null, right: 5 },
diff --git a/package-lock.json b/package-lock.json
index 3d7e041619..3080ac5966 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -2469,8 +2469,7 @@
     "atob": {
       "version": "2.1.2",
       "resolved": "https://registry.npmjs.org/atob/-/atob-2.1.2.tgz",
-      "integrity": "sha512-Wm6ukoaOGJi/73p/cl2GvLjTI5JM1k/O14isD73YML8StrH/7/lRFgmg8nICZgD3bZZvjwCGxtMOD3wWNAu8cg==",
-      "dev": true
+      "integrity": "sha512-Wm6ukoaOGJi/73p/cl2GvLjTI5JM1k/O14isD73YML8StrH/7/lRFgmg8nICZgD3bZZvjwCGxtMOD3wWNAu8cg=="
     },
     "aws-sign2": {
       "version": "0.7.0",
@@ -4117,7 +4116,8 @@
       "version": "1.3.0",
       "resolved": "https://registry.npmjs.org/growly/-/growly-1.3.0.tgz",
       "integrity": "sha1-8QdIy+dq+WS3yWyTxrzCivEgwIE=",
-      "dev": true
+      "dev": true,
+      "optional": true
     },
     "har-schema": {
       "version": "2.0.0",
@@ -4657,6 +4657,7 @@
       "resolved": "https://registry.npmjs.org/is-wsl/-/is-wsl-2.2.0.tgz",
       "integrity": "sha512-fKzAra0rGJUUBwGBgNkHZuToZcn+TtXHpeCgmkMJMMYx1sQDYaCSyjJBSCa2nH1DGm7s3n1oBnohoVTBaN7Lww==",
       "dev": true,
+      "optional": true,
       "requires": {
         "is-docker": "^2.0.0"
       }
@@ -7187,6 +7188,7 @@
       "resolved": "https://registry.npmjs.org/lru-cache/-/lru-cache-6.0.0.tgz",
       "integrity": "sha512-Jo6dJ04CmSjuznwJSS3pUeWmd/H0ffTlkXXgwZi+eq1UCmqQwCh+eLsYOYCwY991i2Fah4h1BEMCx4qThGbsiA==",
       "dev": true,
+      "optional": true,
       "requires": {
         "yallist": "^4.0.0"
       }
@@ -7380,6 +7382,7 @@
       "resolved": "https://registry.npmjs.org/node-notifier/-/node-notifier-8.0.1.tgz",
       "integrity": "sha512-BvEXF+UmsnAfYfoapKM9nGxnP+Wn7P91YfXmrKnfcYCx6VBeoN5Ez5Ogck6I8Bi5k4RlpqRYaw75pAwzX9OphA==",
       "dev": true,
+      "optional": true,
       "requires": {
         "growly": "^1.3.0",
         "is-wsl": "^2.2.0",
@@ -7394,6 +7397,7 @@
           "resolved": "https://registry.npmjs.org/semver/-/semver-7.3.4.tgz",
           "integrity": "sha512-tCfb2WLjqFAtXn4KEdxIhalnRtoKFN7nAwj0B3ZXCbQloV2tq5eDbcTmT68JJD3nRJq24/XgxtQKFIpQdtvmVw==",
           "dev": true,
+          "optional": true,
           "requires": {
             "lru-cache": "^6.0.0"
           }
@@ -7402,13 +7406,15 @@
           "version": "8.3.2",
           "resolved": "https://registry.npmjs.org/uuid/-/uuid-8.3.2.tgz",
           "integrity": "sha512-+NYs2QeMWy+GWFOEm9xnn6HCDp0l7QBD7ml8zLUmJ+93Q5NF0NocErnwkTkXVFNiX3/fpC6afS8Dhb/gz7R7eg==",
-          "dev": true
+          "dev": true,
+          "optional": true
         },
         "which": {
           "version": "2.0.2",
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@@ -8543,7 +8549,8 @@
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@@ -9553,7 +9560,8 @@
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-      "dev": true
+      "dev": true,
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