JS ES6 Features vs Tradational way - Part 1
Tags: webdev, javascript, es6, beginners
Published: 2024-02-03 03:16:58


These examples showcase the usage of various ES6 features for more concise and readable code.

1. **Popular Features of ES6:**
   ES6, or ECMAScript 2015, introduced several features to enhance JavaScript. Some popular features include:
   - **let and const:** Block-scoped variable declarations.
   - **Arrow Functions:** Concise syntax for function expressions.
   - **Classes:** Syntactical sugar over the prototype-based inheritance.
   - **Template Literals:** Enhanced string interpolation.
   - **Destructuring:** Extracting values from arrays or objects.
   - **Default Parameters:** Assigning default values to function parameters.
   - **Rest Parameter:** Representing an indefinite number of arguments as an array.
   - **Spread Operator:** Spreading elements of an array or object.
   - **Promises:** Handling asynchronous operations more effectively.
   - **Modules:** Encapsulation and organization of code in separate files.
Certainly! Here are examples demonstrating each of the mentioned features in ES6:

1. **let and const:**
```javascript
let x = 10;
const PI = 3.1415;

x = 20; // Valid for let
// PI = 3.14; // Error, const cannot be reassigned
```

2. **Arrow Functions:**
```javascript
// Regular function
function add(a, b) {
  return a + b;
}

// Arrow function
const addArrow = (a, b) => a + b;
```

3. **Classes:**
```javascript
class Animal {
  constructor(name) {
    this.name = name;
  }

  speak() {
    console.log(`${this.name} makes a sound`);
  }
}

const dog = new Animal('Dog');
dog.speak(); // Output: Dog makes a sound
```

4. **Template Literals:**
```javascript
const name = 'John';
const greeting = `Hello, ${name}!`;
console.log(greeting); // Output: Hello, John!
```

5. **Destructuring:**
```javascript
const person = { name: 'Alice', age: 30 };
const { name, age } = person;
console.log(name, age); // Output: Alice 30
```

6. **Default Parameters:**
```javascript
function greet(name = 'Guest') {
  console.log(`Hello, ${name}!`);
}

greet(); // Output: Hello, Guest!
greet('Bob'); // Output: Hello, Bob!
```

7. **Rest Parameter:**
```javascript
function sum(...numbers) {
  return numbers.reduce((acc, num) => acc + num, 0);
}

console.log(sum(1, 2, 3)); // Output: 6
```

8. **Spread Operator:**
```javascript
const array1 = [1, 2, 3];
const array2 = [...array1, 4, 5];

console.log(array2); // Output: [1, 2, 3, 4, 5]
```

9. **Promises:**
```javascript
const fetchData = () => {
  return new Promise((resolve, reject) => {
    // Simulating asynchronous operation
    setTimeout(() => {
      const data = 'Some data';
      resolve(data);
      // reject('Error occurred'); // Uncomment to simulate rejection
    }, 1000);
  });
};

fetchData()
  .then(data => console.log(data))
  .catch(error => console.error(error));
```

10. **Modules:**
```javascript
// file1.js
export const add = (a, b) => a + b;

// file2.js
import { add } from './file1.js';

console.log(add(3, 4)); // Output: 7
```
2. **Object-Oriented Features in ES6:**
   ES6 supports several object-oriented features, including:
   - **Classes and Constructors:** A more structured way to define and instantiate objects.
   - **Inheritance:** The `extends` keyword facilitates prototype-based inheritance.
   - **Getter and Setter Methods:** Control access to object properties.
   - **Static Methods:** Methods that belong to the class rather than instances.
   - **Super Keyword:** Refers to the parent class.

Certainly. Below is an equivalent example in JavaScript using ES6 syntax:

```javascript
// Class definition with a constructor
class Vehicle {
    constructor(brand) {
        this.brand = brand;
    }

    // Getter method
    getBrand() {
        return this.brand;
    }

    // Setter method
    setBrand(brand) {
        this.brand = brand;
    }

    // Static method
    static displayInfo() {
        console.log("This is a Vehicle class.");
    }
}

// Subclass inheriting from Vehicle
class Car extends Vehicle {
    constructor(brand, year) {
        super(brand);
        this.year = year;
    }

    // Overriding the getter method from the parent class
    getBrand() {
        return `Car brand: ${super.getBrand()}`;
    }
}

// Instantiating an object of the Car class
const myCar = new Car("Toyota", 2022);

// Accessing and displaying information using getter methods
console.log(`Brand: ${myCar.getBrand()}`);
console.log(`Year: ${myCar.year}`);

// Using a static method of the parent class
Vehicle.displayInfo();
```

In this JavaScript ES6 example:

1. The `Vehicle` class and its methods are defined using the class syntax.
2. The `Car` class extends `Vehicle` and utilizes the `super` keyword in its constructor.
3. The getter method in the `Car` class overrides the one in the parent class, demonstrating polymorphism.
4. The `Main` part of the example showcases instantiation of a `Car` object and accessing its properties and methods.

3. **Comparison Between ES5 and ES6:**
   - ES6 introduced let and const for block-scoped variables, whereas ES5 primarily used var.
   - ES6 provides arrow functions, making syntax concise for function expressions.
   - ES6 introduced classes, enhancing object-oriented programming.
   - Template literals in ES6 simplify string interpolation compared to concatenation in ES5.
   - Destructuring and default parameters enhance code readability in ES6.
   - Promises in ES6 offer a cleaner alternative to callback-based asynchronous operations.

Certainly. Let's provide concise code examples to illustrate the mentioned ES5 and ES6 features:

1. **Block-Scoped Variables (var vs. let/const):**
   
   ES5 (var):
   ```javascript
   for (var i = 0; i < 5; i++) {
       // Some code
   }
   console.log(i); // Outputs: 5
   ```

   ES6 (let/const):
   ```javascript
   for (let j = 0; j < 5; j++) {
       // Some code
   }
   console.log(j); // ReferenceError: j is not defined
   ```

2. **Arrow Functions:**

   ES5:
   ```javascript
   var add = function(a, b) {
       return a + b;
   };
   ```

   ES6:
   ```javascript
   const add = (a, b) => a + b;
   ```

3. **Classes:**

   ES5 (Prototype-based approach):
   ```javascript
   function Car(brand) {
       this.brand = brand;
   }

   Car.prototype.getBrand = function() {
       return this.brand;
   };

   var myCar = new Car('Toyota');
   ```

   ES6:
   ```javascript
   class Car {
       constructor(brand) {
           this.brand = brand;
       }

       getBrand() {
           return this.brand;
       }
   }

   const myCar = new Car('Toyota');
   ```

4. **Template Literals:**

   ES5:
   ```javascript
   var name = 'John';
   console.log('Hello, ' + name + '!');
   ```

   ES6:
   ```javascript
   const name = 'John';
   console.log(`Hello, ${name}!`);
   ```

5. **Destructuring and Default Parameters:**

   ES5:
   ```javascript
   function processData(data) {
       var username = data.username || 'Guest';
       var age = data.age || 25;
       // Some code
   }
   ```

   ES6:
   ```javascript
   function processData({ username = 'Guest', age = 25 }) {
       // Some code
   }
   ```

6. **Promises:**

   ES5 (Callback-based):
   ```javascript
   function fetchData(callback) {
       // Asynchronous operation
       setTimeout(function() {
           callback('Data received');
       }, 1000);
   }

   fetchData(function(data) {
       console.log(data);
   });
   ```

   ES6 (Promise-based):
   ```javascript
   function fetchData() {
       return new Promise(function(resolve) {
           // Asynchronous operation
           setTimeout(function() {
               resolve('Data received');
           }, 1000);
       });
   }

   fetchData().then(function(data) {
       console.log(data);
   });
   ```

These examples showcase the evolution and simplification of code in ES6 compared to its predecessor, ES5.

4. **let vs. const vs. var:**
   - **let:** Allows reassignment, block-scoped.
   - **const:** Does not allow reassignment, block-scoped.
   - **var:** Function-scoped, allows redeclaration and reassignment.

5. **Arrow Function:**
   - Arrow functions provide a concise syntax for writing function expressions.
   - They lexically bind the `this` value, avoiding the need for the `function` keyword.
   - Ideal for shorter functions and anonymous functions.

6. **When Not to Use Arrow Functions:**
   - Avoid arrow functions when dynamic context binding (`this`) is needed.
   - Not suitable for methods within objects due to lexical `this`.
Arrow functions in JavaScript offer concise syntax and lexical scoping but are not suitable for all scenarios. One should be cautious when using arrow functions in the following situations:
 Certainly. Let's provide examples illustrating both correct and erroneous use of arrow functions in the mentioned scenarios:

1. **Methods within Objects:**

   Correct Use:
   ```javascript
   const person = {
       name: 'John',
       sayHello: function() {
           console.log(`Hello, ${this.name}`);
       }
   };
   person.sayHello(); // Outputs: Hello, John
   ```

   Erroneous Use:
   ```javascript
   const person = {
       name: 'John',
       sayHello: () => {
           console.log(`Hello, ${this.name}`);
       }
   };
   person.sayHello(); // Outputs: Hello, undefined (incorrect behavior)
   ```

2. **Functions Requiring Their Own 'this':**

   Correct Use:
   ```javascript
   const button = document.getElementById('myButton');
   button.addEventListener('click', function() {
       console.log('Button clicked:', this); // 'this' refers to the button element
   });
   ```

   Erroneous Use:
   ```javascript
   const button = document.getElementById('myButton');
   button.addEventListener('click', () => {
       console.log('Button clicked:', this); // 'this' does not refer to the button element
   });
   ```

3. **Constructor Functions:**

   Correct Use:
   ```javascript
   function MyObject() {
       this.value = 42;
   }
   const obj = new MyObject();
   ```

   Erroneous Use:
   ```javascript
   const MyObject = () => {
       this.value = 42; // 'this' does not bind correctly
   };
   const obj = new MyObject(); // TypeError: MyObject is not a constructor
   ```

4. **Functions with Dynamic 'arguments':**

   Correct Use:
   ```javascript
   function sum() {
       let total = 0;
       for (const arg of arguments) {
           total += arg;
       }
       return total;
   }
   console.log(sum(1, 2, 3)); // Outputs: 6
   ```

   Erroneous Use:
   ```javascript
   const sum = () => {
       let total = 0;
       for (const arg of arguments) { // 'arguments' object is not available in arrow functions
           total += arg;
       }
       return total;
   };
   console.log(sum(1, 2, 3)); // ReferenceError: arguments is not defined
   ```

These examples highlight the correct and erroneous usage of arrow functions in various scenarios, emphasizing the importance of choosing the appropriate function syntax based on the specific requirements of the code.

7. **Generator Function:**
   - A special type of function that can be paused and resumed.
   - Implemented using function `function*` syntax and the **yield **keyword.
   - Useful for asynchronous operations and iterating over large datasets.
Certainly, here's a more straightforward example of a generator function:

```javascript
// Generator function definition
function* simpleGenerator() {
    yield 'First';
    yield 'Second';
    yield 'Third';
}

// Creating a generator object
const generator = simpleGenerator();

// Accessing values using the generator
console.log(generator.next().value); // Outputs: 'First'
console.log(generator.next().value); // Outputs: 'Second'
console.log(generator.next().value); // Outputs: 'Third'
console.log(generator.next().value); // Outputs: undefined
```

Certainly. A generator function is a special type of function in JavaScript that allows you to control the execution flow with the use of the yield keyword. Here's a simple example of a generator function:

javascript
Copy code
// Generator function definition
function* generateNumbers() {
    yield 1;
    yield 2;
    yield 3;
}

// Creating a generator object
const numbersGenerator = generateNumbers();

// Accessing values using the generator
console.log(numbersGenerator.next().value); // Outputs: 1
console.log(numbersGenerator.next().value); // Outputs: 2
console.log(numbersGenerator.next().value); // Outputs: 3
console.log(numbersGenerator.next().value); // Outputs: undefined
In this example:

function* declares a generator function.
yield is used to produce values one at a time.
Each time numbersGenerator.next() is called, the generator function executes until it encounters a yield statement, returning the yielded value.
The generator keeps track of its internal state, allowing you to resume its execution from where it left off.

This example illustrates the basic structure and functionality of a generator function in a more straightforward manner.

8. **Spread Operator:**
   - The spread operator (`...`) expands elements of an iterable (array, string, etc.) into individual elements.
   - Useful for array/object manipulation, function arguments, and creating shallow copies.
Certainly, let's compare the use of the spread operator in ES6 with a more traditional approach.

**ES6 - Spread Operator:**

The spread operator (`...`) in ES6 allows for the expansion of iterable elements, such as arrays or strings. Here's an example:

```javascript
// Using the spread operator to concatenate arrays
const array1 = [1, 2, 3];
const array2 = [4, 5, 6];
const concatenatedArray = [...array1, ...array2];
console.log(concatenatedArray); // Outputs: [1, 2, 3, 4, 5, 6]
```

In this example, the spread operator is used to create a new array (`concatenatedArray`) by combining the elements of `array1` and `array2`.

**Traditional Approach:**

Prior to ES6, you might achieve the same result using methods like `concat` or `slice`:

```javascript
// Using the concat method to concatenate arrays (traditional approach)
const array1 = [1, 2, 3];
const array2 = [4, 5, 6];
const concatenatedArray = array1.concat(array2);
console.log(concatenatedArray); // Outputs: [1, 2, 3, 4, 5, 6]
```

This traditional approach involves using a method (`concat` in this case) to combine arrays.

**ES6 - Spread Operator with Objects:**

The spread operator can also be used with objects to shallow copy and merge them:

```javascript
// Using the spread operator with objects
const obj1 = { a: 1, b: 2 };
const obj2 = { c: 3, d: 4 };
const mergedObject = { ...obj1, ...obj2 };
console.log(mergedObject); // Outputs: { a: 1, b: 2, c: 3, d: 4 }
```

**Traditional Approach with Objects:**

A traditional approach might involve using a loop or methods like `Object.assign`:

```javascript
// Using Object.assign to merge objects (traditional approach)
const obj1 = { a: 1, b: 2 };
const obj2 = { c: 3, d: 4 };
const mergedObject = Object.assign({}, obj1, obj2);
console.log(mergedObject); // Outputs: { a: 1, b: 2, c: 3, d: 4 }
```

The spread operator in ES6 provides a more concise and readable syntax for achieving similar operations, especially when working with arrays and objects.

9. **Destructuring in ES6:**
   - A concise way to extract values from arrays or properties from objects.
   - Enhances readability and simplifies assignment.

Destructuring assignment in ES6 allows for the extraction of values from arrays or properties from objects in a concise and readable manner. Let's compare it with more traditional approaches.

**ES6 - Destructuring in Arrays:**

```javascript
// Destructuring assignment in arrays
const numbers = [1, 2, 3, 4, 5];

// Extracting values using destructuring
const [first, second, ...rest] = numbers;

console.log(first); // Outputs: 1
console.log(second); // Outputs: 2
console.log(rest); // Outputs: [3, 4, 5]
```

**Traditional Approach - Arrays:**

In a more traditional approach, you might access array elements using indexing:

```javascript
// Accessing array elements using indexing (traditional approach)
const numbers = [1, 2, 3, 4, 5];

const first = numbers[0];
const second = numbers[1];
const rest = numbers.slice(2);

console.log(first); // Outputs: 1
console.log(second); // Outputs: 2
console.log(rest); // Outputs: [3, 4, 5]
```

**ES6 - Destructuring in Objects:**

```javascript
// Destructuring assignment in objects
const person = { name: 'John', age: 30, city: 'New York' };

// Extracting properties using destructuring
const { name, age, country = 'USA' } = person;

console.log(name); // Outputs: John
console.log(age); // Outputs: 30
console.log(country); // Outputs: USA (default value assigned)
```

**Traditional Approach - Objects:**

In a traditional approach, you might access object properties using dot notation:

```javascript
// Accessing object properties using dot notation (traditional approach)
const person = { name: 'John', age: 30, city: 'New York' };

const name = person.name;
const age = person.age;
const country = person.country || 'USA';

console.log(name); // Outputs: John
console.log(age); // Outputs: 30
console.log(country); // Outputs: USA (default value assigned)
```

Destructuring in ES6 provides a cleaner and more concise syntax, especially when dealing with complex data structures. It allows for better readability and reduces the need for repetitive syntax seen in traditional approaches.

10. **Promises in ES6:**
    - Objects representing the eventual completion or failure of an asynchronous operation.
    - Consists of `resolve` and `reject` functions, handling success and failure scenarios.
    - Easier handling of asynchronous code compared to callbacks.

11. **Rest Parameter in ES6:**
    - Allows representing an indefinite number of function arguments as an array.
    - Improves flexibility in function declarations by handling variable-length argument lists.
The rest parameter in ES6 allows functions to accept an indefinite number of arguments as an array. Let's compare its usage with a more traditional approach.

**ES6 - Rest Parameter:**

```javascript
// Rest parameter in ES6
function sum(...numbers) {
    return numbers.reduce((acc, num) => acc + num, 0);
}

console.log(sum(1, 2, 3, 4)); // Outputs: 10
```

In this example, the `...numbers` syntax is used as the rest parameter, collecting any number of arguments passed to the function into the `numbers` array.

**Traditional Approach:**

In a more traditional approach, you might use the `arguments` object:

```javascript
// Using arguments object (traditional approach)
function sum() {
    const args = Array.from(arguments);
    return args.reduce((acc, num) => acc + num, 0);
}

console.log(sum(1, 2, 3, 4)); // Outputs: 10
```

Here, `arguments` is converted to an array using `Array.from(arguments)`. This is necessary because the `arguments` object is array-like but not a real array.

**Note:**
1. The rest parameter allows for a more straightforward and intuitive syntax for collecting variable arguments.
2. The `arguments` object is not a true array, and using it involves additional steps for conversion.

The rest parameter in ES6 provides a more modern and concise way to handle variable arguments in functions. It is especially beneficial when dealing with functions that need to accept an unspecified number of parameters.

12. **Template Literals in ES6:**
    - Strings enclosed by backticks (``) that allow embedded expressions.
    - Improve code readability and simplify string concatenation compared to traditional methods.
Template literals in ES6 provide a more concise and expressive way to work with strings compared to traditional string concatenation or interpolation methods. Let's compare the usage of template literals with a more traditional approach.

**ES6 - Template Literals:**

```javascript
// Template literals in ES6
const name = 'John';
const age = 30;

const greeting = `Hello, my name is ${name} and I am ${age} years old.`;

console.log(greeting); // Outputs: Hello, my name is John and I am 30 years old.
```

In this example, the `${}` syntax within backticks allows for the easy embedding of variables and expressions directly into the string.

**Traditional Approach:**

In a more traditional approach, you might use string concatenation or string interpolation:

```javascript
// Using string concatenation and interpolation (traditional approach)
const name = 'John';
const age = 30;

const greeting = 'Hello, my name is ' + name + ' and I am ' + age + ' years old.';

console.log(greeting); // Outputs: Hello, my name is John and I am 30 years old.
```

Or, using string interpolation in older JavaScript versions:

```javascript
// Using string interpolation in older JavaScript versions (traditional approach)
const name = 'John';
const age = 30;

const greeting = 'Hello, my name is ' + name + ' and I am ' + age + ' years old.';

console.log(greeting); // Outputs: Hello, my name is John and I am 30 years old.
```

**Key Differences:**
1. Template literals offer a cleaner and more readable syntax for string interpolation, especially when dealing with multiple variables or expressions.
2. They allow for the easy inclusion of line breaks within the string.

Overall, template literals in ES6 enhance the way strings are handled in JavaScript, providing a more modern and flexible approach compared to traditional string concatenation.

13. **Why Use ES6 Classes:**
    - Provides a more intuitive and structured syntax for object-oriented programming.
    - Encourages code organization and reuse through inheritance.
**Why Use ES6 Classes:**

1. **Intuitive and Structured Syntax:**
   - **ES6 Classes:**
     ```javascript
     class Car {
         constructor(brand) {
             this.brand = brand;
         }

         displayInfo() {
             console.log(`Brand: ${this.brand}`);
         }
     }
     ```
   - **Traditional Way:**
     ```javascript
     function Car(brand) {
         this.brand = brand;
     }

     Car.prototype.displayInfo = function() {
         console.log('Brand: ' + this.brand);
     };
     ```

   ES6 classes provide a more intuitive and concise syntax for defining classes, making the code structure clearer and more aligned with the expectations of developers familiar with class-based languages.

2. **Encourages Code Organization and Reuse through Inheritance:**
   - **ES6 Classes:**
     ```javascript
     class Vehicle {
         constructor(type) {
             this.type = type;
         }

         displayType() {
             console.log(`Type: ${this.type}`);
         }
     }

     class Car extends Vehicle {
         constructor(brand, type) {
             super(type);
             this.brand = brand;
         }

         displayInfo() {
             console.log(`Brand: ${this.brand}`);
         }
     }
     ```
   - **Traditional Way:**
     ```javascript
     function Vehicle(type) {
         this.type = type;
     }

     Vehicle.prototype.displayType = function() {
         console.log('Type: ' + this.type);
     };

     function Car(brand, type) {
         Vehicle.call(this, type);
         this.brand = brand;
     }

     Car.prototype = Object.create(Vehicle.prototype);
     Car.prototype.constructor = Car;

     Car.prototype.displayInfo = function() {
         console.log('Brand: ' + this.brand);
     };
     ```

   ES6 classes simplify the process of inheritance, making it more readable and reducing the boilerplate code required in the traditional prototype-based approach. This encourages the creation of well-organized and reusable code.

In summary, using ES6 classes provides a cleaner, more readable syntax for object-oriented programming, making code organization and reuse through inheritance more straightforward compared to the traditional prototype-based approach.

14. **Creating a Class in ES6:**
    - Use the `class` keyword followed by a class name.
    - Define a constructor method for initializing instances.
    - Add methods within the class for functionality.
**Creating a Class in ES6:**

```javascript
// ES6 Class
class Animal {
    constructor(name, sound) {
        this.name = name;
        this.sound = sound;
    }

    makeSound() {
        console.log(`${this.name} says ${this.sound}`);
    }
}

// Creating an instance of the class
const dog = new Animal('Dog', 'Woof');
dog.makeSound(); // Outputs: Dog says Woof
```

**Traditional Way (Constructor Function and Prototypes):**

```javascript
// Constructor Function
function Animal(name, sound) {
    this.name = name;
    this.sound = sound;
}

// Prototype Method
Animal.prototype.makeSound = function() {
    console.log(this.name + ' says ' + this.sound);
};

// Creating an instance of the constructor function
const dog = new Animal('Dog', 'Woof');
dog.makeSound(); // Outputs: Dog says Woof
```

**Key Differences:**

1. **Syntax:**
   - ES6 classes provide a more concise and expressive syntax for defining classes.
   - The traditional approach involves using a constructor function and defining methods on the prototype.

2. **Class Inheritance:**
   - ES6 classes have a built-in `extends` keyword for class inheritance.
   - In the traditional approach, you need to use the `prototype` chain for inheritance.

3. **Constructor:**
   - In ES6 classes, the constructor is defined using the `constructor` method.
   - In the traditional approach, the constructor is the function itself.

4. **Readability:**
   - ES6 classes offer improved readability, especially for developers familiar with class-based languages.
   - The traditional approach may involve more boilerplate code and may be less intuitive for those new to JavaScript.

5. **Syntactic Sugar:**
   - ES6 classes are considered syntactic sugar over the traditional prototype-based approach, providing a more convenient and modern syntax.

In summary, while both approaches achieve the same result, ES6 classes offer a cleaner and more intuitive syntax, making the code more readable and aligning it with class-based programming conventions. The traditional prototype-based approach is still relevant, especially in environments without ES6 support. However, ES6 classes are widely adopted for their improved syntax and features.

15. **Class Expression:**
    - Similar to class declaration but can be unnamed.
    - Can be assigned to a variable.
**Class Expression in ES6:**

```javascript
// Class Expression
const Animal = class {
    constructor(name, sound) {
        this.name = name;
        this.sound = sound;
    }

    makeSound() {
        console.log(`${this.name} says ${this.sound}`);
    }
};

// Creating an instance of the class
const dog = new Animal('Dog', 'Woof');
dog.makeSound(); // Outputs: Dog says Woof
```

**Traditional Way (Constructor Function Expression):**

```javascript
// Constructor Function Expression
const Animal = function(name, sound) {
    this.name = name;
    this.sound = sound;
};

// Prototype Method
Animal.prototype.makeSound = function() {
    console.log(this.name + ' says ' + this.sound);
};

// Creating an instance of the constructor function
const dog = new Animal('Dog', 'Woof');
dog.makeSound(); // Outputs: Dog says Woof
```

**Key Differences:**

1. **Syntax:**
   - In ES6, a class expression is used, similar to a class declaration but without a name.
   - The traditional approach involves creating a constructor function expression.

2. **Assignment to a Variable:**
   - Class expressions can be assigned to variables, allowing for flexibility in usage.
   - In the traditional approach, constructor function expressions are also commonly assigned to variables for reuse.

3. **Unnamed:**
   - Class expressions are unnamed, as the class itself is defined in the variable assignment.
   - Constructor function expressions can also be unnamed, depending on how they are used.

4. **Readability:**
   - Class expressions can provide a cleaner syntax when creating classes on the fly or within limited scope.
   - Constructor function expressions are flexible but may involve more verbose syntax.

In summary, class expressions in ES6 offer a concise and flexible way to define classes without the need for a separate declaration. Both class expressions and constructor function expressions are viable options, with the choice depending on specific coding requirements and stylistic preferences.