ES6 introduces a new array method called `map`, using which we can apply a function on every element of an array. This is useful in React because, using a `map`, we can generate lists and repeated elements with a minimal amount of code.


let numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9];
let twosMultiples = numbers.map ((n) => n * 2);
console.log (twosMultiples);

The `map` iterates over the entire array, passing the elements one by one as an argument into the inline function and storing the return values of the inline function into an output array. 

We can use the same logic combined with **JSX** and React to achieve amazing results. We will explore JSX in detail in later chapters.


### Example

There is a popular coding problem called the ‘FizzBuzz’ problem. The user is given an array of integers and asked to go through the array and:
- Replace the element with `"FizzBuzz"` if it's divisible by 3 and 5;
- Replace the element with `"Fizz"` if it's divisible by 3;
- Replace the element with `"Buzz"` if it's divisible by 5;
- Leave the integer as it is if it's divisible by none.

In this section we will explore why React is useful and why it is worth learning it at all. We will also learn one prerequisite, ES6, which will be used throughout the course.

In this section, we will learn another prerequisite - JSX which will be used throughout the course. Finally, we will explore some example code to get acquainted with React.

In this section we will learn about the essential and practical parts of React excluding the components – which will be covered in the next section. We will look at how JSX can be used with React, and how to create and render more complex elements in the React DOM using JSX. We will also learn how to set up a React based project, and we will explore its structure for deepening our understanding.

In this section you’ll be introduced to React components. We will look at what React components are and why we need them. We will explore the two different types of React components and learn the syntax for creating them. We will use them to create a single page application that displays X.

In this section we will learn more about how to combine JavaScript and JSX to create dynamic content. We will also learn how to pass data between components. In the end we will also explore event handling.

In the end of the previous chapter, we tried making a Todo application though in our attempt to do so we soon discovered that we needed some method for re-rendering the components once the data is updated in a component as React wasn’t automatically doing that for us. In this section we will learn how to fix such issues using ‘Hooks’. We will learn and implement hooks in detail. By the end of this section, you will be able to create stateful components in React and combine them to create complex web applications.

In this chapter we will learn how to add different pages to our React application and render different components based on URL. You will gain sufficient knowledge to be able to create multi-page applications.