Executable coding blocks production-readiness - PR 2

README.md

@@ -1494,7 +1494,7 @@ There are multiple ways to iterate over object properties as well as arrays in J
 
 The `for...in` loop iterates over all enumerable properties of an object, including inherited enumerable properties. So it is important to have a check if you only want to iterate over object's own properties
 
-```js
+```js live
 const obj = {
   a: 1,
   b: 2,
@@ -1513,7 +1513,7 @@ for (const key in obj) {
 
 `Object.keys()` returns an array of the object's own enumerable property names. You can then use a for...of loop or forEach to iterate over this array.
 
-```js
+```js live
 const obj = {
   a: 1,
   b: 2,
@@ -1529,7 +1529,7 @@ Most common ways to iterate over array are using `for` loop and `Array.prototype
 
 **Using `for` loop**
 
-```js
+```js live
 let array = [1, 2, 3, 4, 5, 6];
 for (let index = 0; index < array.length; index++) {
   console.log(array[index]);
@@ -1538,7 +1538,7 @@ for (let index = 0; index < array.length; index++) {
 
 **Using `Array.prototype.forEach` method**
 
-```js
+```js live
 let array = [1, 2, 3, 4, 5, 6];
 array.forEach((number, index) => {
   console.log(`${number} at index ${index}`);
@@ -1549,7 +1549,7 @@ array.forEach((number, index) => {
 
 This method is the newest and most convenient way to iterate over arrays. It automatically iterates over each element without requiring you to manage the index.
 
-```js
+```js live
 const numbers = [1, 2, 3, 4, 5];
 
 for (const number of numbers) {
@@ -2322,9 +2322,9 @@ Template literals are a feature in JavaScript that allow for easier string inter
 
 Example:
 
-```js
-const name = 'John';
-const greeting = `Hello, ${name}!`;
+```js live
+const myName = 'John';
+const greeting = `Hello, ${myName}!`;
 console.log(greeting); // Output: Hello, John!
 ```
 
@@ -2365,14 +2365,16 @@ console.log(result); // "Hello world! How are you?"
 
 The spread operator, represented by three dots (`...`), is used in JavaScript to expand iterable objects like arrays or strings into individual elements. It can also be used to spread object properties. For example, you can use it to combine arrays, copy arrays, or pass array elements as arguments to a function.
 
-```js
+```js live
 const arr1 = [1, 2, 3];
 const arr2 = [4, 5, 6];
-const combined = [...arr1, ...arr2]; // [1, 2, 3, 4, 5, 6]
+const combined = [...arr1, ...arr2];
+console.log(combined); // [1, 2, 3, 4, 5, 6]
 
 const obj1 = { a: 1, b: 2 };
 const obj2 = { c: 3, d: 4 };
-const combinedObj = { ...obj1, ...obj2 }; // { a: 1, b: 2, c: 3, d: 4 }
+const combinedObj = { ...obj1, ...obj2 };
+console.log(combinedObj); // { a: 1, b: 2, c: 3, d: 4 }
 ```
 
 <!-- Update here: /questions/what-is-the-spread-operator-and-how-is-it-used/en-US.mdx -->
@@ -2565,16 +2567,17 @@ let b = 10;
 
 To avoid problems related to hoisting, always declare variables at the top of their scope using `let` or `const` instead of `var`. This ensures that variables are block-scoped and not hoisted to the top of their containing function or global scope. Additionally, declare functions before they are called to avoid issues with function hoisting.
 
-```js
+```js live
 // Use let or const
 let x = 10;
 const y = 20;
+console.log(x, y); // Output: 10 20
 
 // Declare functions before calling them
 function myFunction() {
   console.log('Hello, world!');
 }
-myFunction();
+myFunction(); // Output: 'Hello, world!'
 ```
 
 <!-- Update here: /questions/how-can-you-avoid-problems-related-to-hoisting/en-US.mdx -->
@@ -2615,7 +2618,7 @@ There are multiple ways to iterate over object properties as well as arrays in J
 
 The `for...in` loop iterates over all enumerable properties of an object, including inherited enumerable properties. So it is important to have a check if you only want to iterate over object's own properties
 
-```js
+```js live
 const obj = {
   a: 1,
   b: 2,
@@ -2634,7 +2637,7 @@ for (const key in obj) {
 
 `Object.keys()` returns an array of the object's own enumerable property names. You can then use a for...of loop or forEach to iterate over this array.
 
-```js
+```js live
 const obj = {
   a: 1,
   b: 2,
@@ -2650,7 +2653,7 @@ Most common ways to iterate over array are using `for` loop and `Array.prototype
 
 **Using `for` loop**
 
-```js
+```js live
 let array = [1, 2, 3, 4, 5, 6];
 for (let index = 0; index < array.length; index++) {
   console.log(array[index]);
@@ -2659,7 +2662,7 @@ for (let index = 0; index < array.length; index++) {
 
 **Using `Array.prototype.forEach` method**
 
-```js
+```js live
 let array = [1, 2, 3, 4, 5, 6];
 array.forEach((number, index) => {
   console.log(`${number} at index ${index}`);
@@ -2670,7 +2673,7 @@ array.forEach((number, index) => {
 
 This method is the newest and most convenient way to iterate over arrays. It automatically iterates over each element without requiring you to manage the index.
 
-```js
+```js live
 const numbers = [1, 2, 3, 4, 5];
 
 for (const number of numbers) {
@@ -2698,7 +2701,7 @@ There are also other inbuilt methods available which are suitable for specific s
 
 The `break` statement is used to exit a loop or switch statement prematurely, while the `continue` statement skips the current iteration of a loop and proceeds to the next iteration. For example, in a `for` loop, `break` will stop the loop entirely, and `continue` will skip to the next iteration.
 
-```js
+```js live
 for (let i = 0; i < 10; i++) {
   if (i === 5) break; // exits the loop when i is 5
   console.log(i);
@@ -2738,7 +2741,7 @@ The ternary operator is a shorthand for an `if-else` statement in JavaScript. It
 
 To access the index of an element in an array during iteration, you can use methods like `forEach`, `map`, `for...of` with `entries`, or a traditional `for` loop. For example, using `forEach`:
 
-```js
+```js live
 const array = ['a', 'b', 'c'];
 array.forEach((element, index) => {
   console.log(index, element);
@@ -2786,7 +2789,7 @@ switch (expression) {
 
 Rest parameters in JavaScript allow a function to accept an indefinite number of arguments as an array. They are denoted by three dots (`...`) followed by the name of the array. This feature is useful for functions that need to handle multiple arguments without knowing the exact number in advance.
 
-```js
+```js live
 function sum(...numbers) {
   return numbers.reduce((acc, curr) => acc + curr, 0);
 }
@@ -2808,22 +2811,26 @@ console.log(sum(1, 2, 3, 4)); // Output: 10
 
 The spread operator (`...`) in JavaScript allows you to expand elements of an iterable (like an array or object) into individual elements. It is commonly used for copying arrays or objects, merging arrays or objects, and passing elements of an array as arguments to a function.
 
-```js
+```js live
 // Copying an array
 const arr1 = [1, 2, 3];
 const arr2 = [...arr1];
+console.log(arr2); // Output: [1, 2, 3]
 
 // Merging arrays
 const arr3 = [4, 5, 6];
 const mergedArray = [...arr1, ...arr3];
+console.log(mergedArray); // Output: [1, 2, 3, 4, 5, 6]
 
 // Copying an object
 const obj1 = { a: 1, b: 2 };
 const obj2 = { ...obj1 };
+console.log(obj2); // Output: { a: 1, b: 2 }
 
 // Merging objects
 const obj3 = { c: 3, d: 4 };
 const mergedObject = { ...obj1, ...obj3 };
+console.log(mergedObject); // Output: { a: 1, b: 2, c: 3, d: 4 }
 
 // Passing array elements as function arguments
 const sum = (x, y, z) => x + y + z;
@@ -3005,7 +3012,7 @@ A parameter is a variable in the declaration of a function, while an argument is
 
 Hoisting in JavaScript is a behavior where function declarations are moved to the top of their containing scope during the compile phase. This means you can call a function before it is defined in the code. However, this does not apply to function expressions or arrow functions, which are not hoisted in the same way.
 
-```js
+```js live
 // Function declaration
 hoistedFunction(); // Works fine
 function hoistedFunction() {

questions/can-you-offer-a-use-case-for-the-new-arrow-function-syntax-how-does-this-new-syntax-differ-from-other-functions/en-US.mdx

@@ -7,7 +7,7 @@ subtitle: How does this new syntax differ from other functions?
 
 Arrow functions provide a concise syntax for writing functions in JavaScript. They are particularly useful for maintaining the `this` context within methods and callbacks. For example, in an event handler or array method like `map`, arrow functions can simplify the code and avoid issues with `this` binding.
 
-```javascript
+```js live
 const numbers = [1, 2, 3];
 const doubled = numbers.map((n) => n * 2);
 console.log(doubled); // [2, 4, 6]
@@ -21,30 +21,35 @@ console.log(doubled); // [2, 4, 6]
 
 Arrow functions provide a more concise way to write functions. This is especially useful for short functions or callbacks.
 
-```javascript
+```js live
 // Traditional function
 const add = function (a, b) {
   return a + b;
 };
 
 // Arrow function
-const add = (a, b) => a + b;
+const anotherAdd = (a, b) => a + b;
+
+console.log(add(2, 3)); // Output: 5
+console.log(anotherAdd(2, 3)); // Output: 5
 ```
 
 ### Lexical `this` binding
 
 Arrow functions do not have their own `this` context. Instead, they inherit `this` from the surrounding scope. This is particularly useful in methods and callbacks where the `this` context can be tricky.
 
-```javascript
+```js live
 function Timer() {
   this.seconds = 0;
-  setInterval(() => {
-    this.seconds++;
+  this.increment = () => {
+    this.seconds++; // 'this.seconds' is inherited from the outer scope
     console.log(this.seconds);
-  }, 1000);
+  };
 }
 
 const timer = new Timer();
+timer.increment(); // 1
+timer.increment(); // 2
 ```
 
 In the example above, using a traditional function inside `setInterval` would require additional steps to maintain the correct `this` context.
@@ -53,11 +58,11 @@ In the example above, using a traditional function inside `setInterval` would re
 
 Arrow functions are often used in array methods like `map`, `filter`, and `reduce` for cleaner and more readable code.
 
-```javascript
+```js live
 const numbers = [1, 2, 3, 4, 5];
 
 // Traditional function
-const doubled = numbers.map(function (n) {
+const doubledTraditional = numbers.map(function (n) {
   return n * 2;
 });
 
@@ -71,7 +76,7 @@ console.log(doubled); // [2, 4, 6, 8, 10]
 
 Arrow functions can be used in event handlers to maintain the `this` context of the class or object.
 
-```javascript
+```js
 class Button {
   constructor() {
     this.count = 0;

questions/difference-between-function-person-var-person-person-and-var-person-new-person/en-US.mdx

@@ -33,12 +33,12 @@ This code defines a function named `Person` that takes a parameter `name` and as
 
 `const person = Person()` simply invoke the function's code. When you invoke `Person` as a regular function (i.e., without the `new` keyword), the function does not behave as a constructor. Instead, it executes its code and returns `undefined` if no return value is specified and that gets assigned to the variable intended as the instance. Invoking as such is a common mistake if the function is intended to be used as a constructor.
 
-```js
+```js live
 function Person(name) {
   this.name = name;
 }
 
-const person = Person('John');
+const person = Person('John'); // Throws error in strict mode
 console.log(person); // undefined
 console.log(person.name); // Uncaught TypeError: Cannot read property 'name' of undefined
 ```
@@ -49,7 +49,7 @@ In this case, `Person('John')` does not create a new object. The `person` variab
 
 `const person = new Person()` creates an instance of the `Person` object using the new operator, which inherits from `Person.prototype`. An alternative would be to use `Object.create`, such as: `Object.create(Person.prototype)` and `Person.call(person, 'John')` initializes the object.
 
-```js
+```js live
 function Person(name) {
   this.name = name;
 }

questions/explain-how-prototypal-inheritance-works/en-US.mdx

@@ -12,7 +12,7 @@ This behavior simulates classical inheritance, but it is really more of [delegat
 
 Here's an example of prototypal inheritance:
 
-```js
+```js live
 // Parent object constructor.
 function Animal(name) {
   this.name = name;
@@ -60,7 +60,7 @@ Prototypical inheritance is a feature in JavaScript used to create objects that
 
 1. **Prototypes** : Every object in Javascript has a prototype, which is another object. When you create an object using an object literal or a constructor function, the new object is linked to the prototype of its constructor function or the `Object.prototype` if no prototype is specified. This is commonly referenced using `__proto__` or `[[Prototype]]`. You can also get the prototype by using inbuilt method `Object.getPrototypeOf()` and you can set the prototype of an object via `Object.setPrototypeOf()`.
 
-```js
+```js live
 // Define a constructor function
 function Person(name, age) {
   this.name = name;
@@ -104,7 +104,7 @@ console.log(john.sayHello); // undefined
 
 3. **Constructor functions**: JavaScript provides constructor functions to create objects. When a function is used as a constructor with the new keyword, the new object's prototype (`[[Prototype]]`) is set to the constructor's prototype property.
 
-```js
+```js live
 // Define a constructor function
 function Animal(name) {
   this.name = name;
@@ -142,7 +142,7 @@ console.log(fido.fly); // undefined
 
 4. **`Object.create()`**: This method creates a new object with the specified prototype object and properties. It's a straightforward way to set up prototypical inheritance. If you create a object via `Object.create(null)` it will not inherit any properties from `Object.prototype`. This means the object will not have any built-in properties or methods like `toString()`, `hasOwnProperty()`,
 
-```js
+```js live
 // Define a prototype object
 let proto = {
   greet: function () {

questions/explain-the-concept-of-a-callback-function-in-asynchronous-operations/en-US.mdx

@@ -32,7 +32,7 @@ A callback function is a function that is passed as an argument to another funct
 
 ### Example of a synchronous callback
 
-```js
+```js live
 function greet(name, callback) {
   console.log('Hello ' + name);
   callback();
@@ -76,13 +76,11 @@ fetchData((data) => {
 
 When dealing with asynchronous operations, it's important to handle errors properly. A common pattern is to use the first argument of the callback function to pass an error object, if any.
 
-```js
+```js live
 function fetchData(callback) {
-  setTimeout(() => {
-    const error = null;
-    const data = { name: 'John', age: 30 };
-    callback(error, data);
-  }, 1000);
+  // assume asynchronous operation to fetch data
+  const { data, error } = { data: { name: 'John', age: 30 }, error: null };
+  callback(error, data);
 }
 
 fetchData((error, data) => {