What was once only considered a language to add enhancements and widgets to a web page has since evolved into its own fully-fledged ecosystem. As of the survey of year 2017 ( https://insights.stackoverflow.com/survey/2017 ), it stands as the most popular language in terms of usage on stack overflow with around a million questions tagged on it. There are tons of frameworks and environments to make it possible to run JavaScript almost anywhere. I believe Atwood's law says it best:

While this quote dates back to 2007, it's never been truer than today. Not only can you use JavaScript to develop a complete single-page application such as Gmail, but you will also see how we can use it to achieve the following projects in the coming chapters of the book:

• Completely power the backend using Node.js and Express.js
• Persist data with a powerful document oriented database such as MongoDB
• Write dynamic HTML pages using Handlebars.js
• Deploy your entire project to the cloud using services such as Heroku and Amazon Web Services (AWS)

With the introduction of Node.js, JavaScript has officially gone in a direction that was never even possible before. Now, you can use JavaScript on the server and you can also use it to develop full-scale, enterprise-level applications. When you combine this with the power of MongoDB and its JSON-powered data, you can work with JavaScript in every layer of your application.

Let's quickly go through some basic concepts of Node.js and MongoDB, which will help you in following the rest of the chapters in this book.