Replace variable declared with var to modern let and const

JavaScript_Advance/callback.js

@@ -62,7 +62,7 @@ transformNumber(10, (num) => {
   * passed to the `resolve()` function, will get passed to the function passed to `.then()`
   * function. Look at the following example from MDN official documents:
   */
-var p1 = new Promise((resolve, reject) => {
+const p1 = new Promise((resolve, reject) => {
   resolve("Success!");
   // or
   // reject(new Error("Error!"));

JavaScript_Advance/cookies.js

@@ -6,7 +6,7 @@ console.log("Simple usage:" + document.cookie);
 // #2 Get a cookie with the name 'actor'
 document.cookie = "movie=Jungle Book";
 document.cookie = "actor=Balu";
-var cookieValue = document.cookie.replace(/(?:(?:^|.*;\s*)actor\s*\=\s*([^;]*).*$)|^.*$/, "$1");
+const cookieValue = document.cookie.replace(/(?:(?:^|.*;\s*)actor\s*\=\s*([^;]*).*$)|^.*$/, "$1");
 console.log("Cookie with the name 'actor':" + cookieValue);
 
 // #3 Set cookie and execute code only once if cookie doesn't exist yet

JavaScript_Advance/do_while_loop.js

@@ -10,7 +10,7 @@ do {
 
  */
 
-var n = 1;
+let n = 1;
 
 do {
   console.log("n is less than 6. n = " + n);

JavaScript_Advance/while_loop.js

@@ -10,7 +10,7 @@
 
  */
 
-var n = 1;
+let n = 1;
 
 while (n < 6) {
   console.log("n is less than 6. n = " + n);

JavaScript_Basics/arrays.js

@@ -27,26 +27,26 @@ console.log(easyMethod);
 // Output [ 'Swapnil Satish Shinde', 76, true ]
 
 // The pop() method removes the last element from an array:
-var fruits = ["Banana", "Orange", "Apple", "Mango"];
+const fruits = ["Banana", "Orange", "Apple", "Mango"];
 fruits.pop(); // Removes the last element ("Mango") from fruits and output is ["Banana","Orange","Apple"]
 
 // Shifting is equivalent to popping, working on the first element instead of the last.
 // The shift() method removes the first array element and "shifts" all other elements to a lower index.
-var cars = ["Acura", "Audi", "Bugatti", "Honda"];
+const cars = ["Acura", "Audi", "Bugatti", "Honda"];
 cars.shift(); // Removes the first element ("Acura") from cars and output is ["Audi","Bugatti","Honda"]
 
 // The length property provides an easy way to append a new element to an array:
-var mobiles = ["Apple", "Nokia", "Samsung", "Sony"];
+const mobiles = ["Apple", "Nokia", "Samsung", "Sony"];
 mobiles[mobiles.length] = "HTC"; // Appends "HTC" to mobiles and output is ["Apple", "Nokia", "Samsung", "Sony", "HTC"]
 
 // delete will delete the object property, but will not reindex the array or update its length. This makes it appears as if it is undefined:
-var myArray = ["a", "b", "c", "d"];
+const myArray = ["a", "b", "c", "d"];
 delete myArray[0];
 "The first value is: " + myArray[0]; // The first value is: undefined
 // Using delete may leave undefined holes in the array. Use pop() or shift() instead.
 
 // The splice() method removes items from array and/or adds items to array and returns the removed items:
-var names = ["Anne", "Belle", "Chloe", "Diane", "Ella", "Frances"];
+const names = ["Anne", "Belle", "Chloe", "Diane", "Ella", "Frances"];
 names.splice(4, 1);
 // This removes 1 item from index 4
 // returns "Ella"

JavaScript_Basics/bugs.js

@@ -1,8 +1,8 @@
-var obj = {
+const obj = {
   name: "Some name"
 };
 
-var name = null;
+const name = null;
 
 console.log(typeof obj); // object;
 console.log(typeof name); // object;

JavaScript_Basics/exercise_1_using_arrays.js

@@ -1,4 +1,4 @@
-var array = [1, 0.16, "Random", function () {
+const array = [1, 0.16, "Random", function () {
   console.log("this is function in an array");
 }, { Key: "Answer" }, false];
 

JavaScript_Basics/filter.js

@@ -21,5 +21,5 @@ function isBigEnough (value) {
   return value >= 10;
 }
 
-var filtered = [12, 5, 8, 130, 44].filter(isBigEnough);
+const filtered = [12, 5, 8, 130, 44].filter(isBigEnough);
 // filtered is [12, 130, 44]

JavaScript_Basics/iife.js

@@ -7,6 +7,6 @@ Can be used as shown below:--
 */
 
 (function (value) {
-  var modified = value + 4;
+  const modified = value + 4;
   console.log(modified);
 }(3));

JavaScript_Basics/map.js

@@ -1,5 +1,5 @@
 // Let's create an array of numbers that we want to get the square of each number in the array
-var numbers = [1, 2, 3, 4, 5];
+const numbers = [1, 2, 3, 4, 5];
 
 // pass a function to map
 const square = numbers.map(function (num) {

JavaScript_Basics/reduce.js

@@ -5,11 +5,10 @@ the array to a single value and executes a provided function
 for each value of the array (from left-to-right) and the return
 value of the function is stored in an accumulator.
 */
-var pokemon = ["squirtle", "charmander", "bulbasaur"];
+const pokemon = ["squirtle", "charmander", "bulbasaur"];
 
-var pokeLength =
-  pokemon.reduce(function (previous, current) {
-  	return previous + current.length;
-  }, 0);
+const pokeLength = pokemon.reduce(function (previous, current) {
+  return previous + current.length;
+}, 0);
 
 // Outputs 27

JavaScript_Basics/strict_mode.js

@@ -2,20 +2,20 @@
 // examples taken from: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode
 
 // Assignment to a non-writable global
-var undefined = 5; // throws a TypeError
-var Infinity = 5; // throws a TypeError
+const undefined = 5; // throws a TypeError
+const Infinity = 5; // throws a TypeError
 
 // Assignment to a non-writable property
-var obj1 = {};
+const obj1 = {};
 Object.defineProperty(obj1, "x", { value: 42, writable: false });
 obj1.x = 9; // throws a TypeError
 
 // Assignment to a getter-only property
-var obj2 = { get x () { return 17; } };
+const obj2 = { get x () { return 17; } };
 obj2.x = 5; // throws a TypeError
 
 // Assignment to a new property on a non-extensible object
-var fixed = {};
+const fixed = {};
 Object.preventExtensions(fixed);
 fixed.newProp = "ohai"; // throws a TypeError
 

JavaScript_Basics/this.js

@@ -1,7 +1,7 @@
 console.log(this); // This gives empty object
 // Output {}
 
-var aa = 1;
+const aa = 1;
 console.log(global.aa); // Global scope is accessible to every where
 // Output undefined
 
@@ -19,7 +19,7 @@ console.log(a);
 // console.log(b) // Output ReferenceError: b is not defined as b is defined using let it is going to be declared only in that block
 
 const help = () => {
-  var a = 4;
+  const a = 4;
   const b = 2; // variables defined by let and const are accessible to there scope only
   console.log(a); // This will not get printed unless and until function is called
 };