Javascript Arrow Functions

The Fundamental Concept of Javascript Arrow Functions

function(a) {
  return a + 100;
}

a => a + 100;

When to Use Javascript Arrow Functions

• Single line callbacks: Arrow functions are perfect for single line callback functions that only include a return statement. With their shorter syntax, your JavaScript code becomes more readable and compact.
• Lexical 'this': If you always need to bind 'this', using the Arrow Function is a good choice because the function does not generate its own 'this' context.

Common Misconceptions about Javascript Arrow Functions

Javascript Arrow Function vs Function: A Comparative Analysis

Similarities Between Javascript Arrow Functions and Classic Functions

function add(a, b) {
  return a + b;
}

let add = (a, b) => a + b;

Differences in Syntax: Javascript Arrow Function vs Function

Use Case Scenarios: Javascript Arrow Function and Regular Function

• When writing functions that will be used as constructors to create new objects with the new keyword, traditional functions are necessary because arrow functions do not support new.
• If your function needs to include a method called super, which allows you to use methods of the parent class in the child class, you cannot use arrow functions because they do not have a prototype and hence cannot call super.
• Traditional functions also allow overloading based on the number of arguments, thanks to the arguments keyword, which is not available in arrow functions.

Exploring the Syntax of Javascript Arrow Functions

Importance of Correct Javascript Arrow Function Syntax

Common Syntax Errors in Javascript Arrow Functions

const foo = a, b => a + b; // incorrect
const foo = (a, b) => a + b; // correct

let add = (a, b) => { // multi-line arrow function
  let sum = a + b;
} // incorrect as there is no return statement

let add = (a, b) => { // multi-line arrow function
  let sum = a + b;
  return sum; // correct
}

Syntax Examples: Unravelling Javascript Arrow Function Syntax

let square=x => x*x;

let add = (a, b) => a + b;

let greet = () => console.log('Hello World');

let double = (x) => 2 * x;

let add = (a, b) => {
  console.log('Addition function called!');
  return a + b;
};

Delving into Async Arrow Function in Javascript

Breaking down Async Arrow Function in Javascript

let myAsyncFunction = async () => {
  // asynchronous code here
};

• It ensures that the function always returns a promise: If a function that is marked as async does not return a value, or if it returns a non-promise value, JavaScript automatically wraps that value in a resolved promise.
• It allows the await keyword to be used in the function: The await operator is used to pause and resume a JavaScript async function and to wait for a promise's resolution or rejection.

Role of Async Arrow Functions in Javascript Programming

Common Applications of Async Arrow Function in Javascript

let fetchData = async() => {
  let response = await fetch('https://api.example.com/data');
  let data = await response.json();
  return data;
};

let delay = async() => {
  await new Promise(resolve => setTimeout(resolve, 5000));
  console.log('This message is displayed after a 5 seconds delay.');
};

let example = async () => {
    let promise = new Promise((resolve, reject) => {
        setTimeout(() => resolve("Promise resolved!"), 2000)
    });

    let result = await promise; 
    console.log(result); // "Promise resolved!"
}
example();

Array map and Javascript Arrow Functions

Understanding Array Map with Javascript Arrow Function

let newArray = oldArray.map((item) => {
  // transformation
  return newValue;
});

let numbers = [1, 2, 3, 4, 5];
let doubled = numbers.map((number) => number * 2);
console.log(doubled); // [2, 4, 6, 8, 10]

Practical Applications: Array Map with Javascript Arrow Function

let values = [1, 2, 3, 4];
let doubleValues = values.map(value => value * 2);

let users = [{name: 'Alice', age: 25}, {name: 'Bob', age: 30}];
let names = users.map(user => user.name);

let pets = [{name: 'Fluffy', type: 'Dog'}, {name: 'Felix', type: 'Cat'} ];
let petDescriptions = pets.map(pet => `${pet.name} is a very cute ${pet.type}`);

Manipulating Arrays: Javascript Arrow Function in Practice

let prices = [100, 200, 300, 400, 500];
let discounted = prices.map(price => price - price * 0.2);

let products = ['Milk', 'Eggs' , 'Bread'];
let prices = [1.50, 2.50, 0.90];
let productsWithPrices = products.map((product, index) => {
  return { name: product, price: prices[index] }
});

Javascript Arrow Functions in Classes and Nesting

Incorporating Arrow Function in Class Javascript

class Counter {
  constructor() {
    this.value = 0;
  }

  increment() {
    this.value++;  
  }
}

let myCounter = new Counter();
setTimeout(myCounter.increment, 1000);

class Counter {
  constructor() {
    this.value = 0;
  }

  increment = () => {
    this.value++;  
  }
}

let myCounter = new Counter();
setTimeout(myCounter.increment, 1000);

Advantages of Using Arrow Function in Class Javascript

• Automatically binding 'this': With arrow functions, this is lexically bound. It means that it uses this from the code that contains the arrow function.
• Simpler syntax: Arrow functions have a shorter syntax compared to function expressions. This results in less code and potentially less confusion.
• Non-binding of arguments: Arrow functions do not have their arguments object. Thus, they are a great choice for functions you plan to use as methods inside a class.

Real-life Scenarios: Nested Arrow Functions in Javascript

app.use((req, res, next) => {
  return (stuff) => {
    // Do something with 'stuff'
    next();
  };
});

let multiply = x => y => x * y;
let double = multiply(2);
let result = double(3); // 6

Understanding the Benefits and Uses of JavaScript Arrow Functions

Broad Advantages of Arrow Function in Javascript

• Succinct Syntax: Arrow functions can reduce the verbosity of your JavaScript code. The code looks cleaner.
• Lexical Scoping: Arrow functions use lexical scoping for the special variable 'this'. 'This' always represents the object that defined the arrow function.
• No Arguments Object: Arrow functions do not have the local variable arguments like regular functions.
• Implicit Returns: If the function body contains only a single statement, you can omit the 'return' keyword and the braces, making your code even more concise.

Specific Use-Case Benefits of Arrow Function in JavaScript

document.getElementById('myButton').addEventListener(
  'click',
  event => {
    // 'this' here is lexically bound from surrounding scope.
    console.log(this);  
  });

let names = ['Alice', 'Bob', 'Charlie'];
let greetings = names.map(name => `Hello, ${name}`);

let numbers = [19, 3, 81, 1, 24, 21];
numbers.sort((a, b) => a - b);

Exploiting the Benefits of Nested Arrow Functions in Javascript

let greeting = language => name => `Hello, ${name}. Welcome to learning ${language}`;
let greetingInSpanish = greeting('Spanish');
console.log(greetingInSpanish('John')); // Hello, John. Welcome to learning Spanish

let add = a => b => a + b;
let addFive = add(5);
console.log(addFive(3)); // 8