What is arrow function in javascript?

An arrow function is a concise way of declaring functions in JavaScript. It uses an arrow (=>) to replace the traditional function keyword, and provides a more concise syntax for defining functions.

Arrow functions are particularly useful in situations where you want to write a one-liner function, such as when using .map(), .filter(), or .reduce() to transform arrays, or when using anonymous functions as callbacks. They also have a lexical this binding, meaning that this refers to the surrounding scope, which can simplify code in certain situations where this would otherwise be dynamically scoped.

For example, consider the following code that uses an anonymous function as a callback in .map():

const numbers = [1, 2, 3, 4];
const doubled = numbers.map(function(number) {
  return number * 2;
});

The same code can be written using an arrow function:

const numbers = [1, 2, 3, 4];
const doubled = numbers.map(number => number * 2);

This concise syntax makes arrow functions a popular choice in modern JavaScript development.