Arrow Functions

It provides a concise syntax for creating functions in JavaScript, written using the => syntax and are especially useful for short, non-method functions.

It looks like this: (arguments) => expression.

It creates a function that accepts arguments and evaluates the expression, returning the result.

For example:

// Arrow function
let multiply = (a, b) => a * b;

console.log(multiply(4, 5)); // Output: 20

// Arrow function with single parameter
let square = x => x * x;

console.log(square(3)); // Output: 9

// Arrow function with no parameters
let greet = () => console.log("Hello!");

greet(); // Output: Hello!

A multiline arrow function in JavaScript allows for the execution of multiple expressions or statements. Unlike single-line arrow functions, multiline arrow functions are enclosed within curly braces {}, and if a return value is desired, an explicit return statement is required.

For example:

const sumOfSquaredEvenNumbers = (arr) => {
  // Filter even numbers
  const evenNumbers = arr.filter(num => num % 2 === 0);
  
  // Square each number
  const squaredNumbers = evenNumbers.map(num => num ** 2);
  
  // Sum the squared values
  const sum = squaredNumbers.reduce((total, num) => total + num, 0);
  
  return sum;
};

const numbers = [1, 2, 3, 4, 5, 6];
console.log(sumOfSquaredEvenNumbers(numbers)); // Output: 56 (2^2 + 4^2 + 6^2 = 4 + 16 + 36 = 56)

In the above example, the arrow function sumOfSquaredEvenNumbers takes an array of numbers arr as input. It first filters out the even numbers, then squares each even number, and finally sums up the squared values using the reduce method.