Introduction to Node.js - What is Node.js?  Currently, on the screen, I have the Chrome console open. For demonstration purposes, I'm going to create a subtract function. function subtract(num0ne, numTwo), and I'm going to {console.log(num0ne - numTwo). Now I'm going to execute the subtract function. subtract, passing into arguments 5 and 3. I will hit 'Enter' to execute.

Now there is a number 2, which is the result in the console. The result was handled by Chrome's JavaScript engine known as the V8 engine, and every browser has its own JavaScript engine. For example, Firefox uses the SpiderMonkey engine, and different JavaScript engines take different approaches on how JavaScript code is executed. When Chrome is given JavaScript code, the browser sends the code to the V8 engine. 

The V8 engine processes the code and returns the results back to the browser. The JavaScript engine is the independent runtime environment in which JavaScript executes. Browser features such as the DOM and Web APIs are provided by the browser and designed to work in conjunction with the JavaScript engine. And this leads to the question, what is Node.js?

Node.js is an open-source, cross-platform, backend JavaScript runtime that runs on the V8 engine and executes JavaScript code outside of the web browser. Meaning we've taken this and turned it into this. And that's it. Thanks for watching at CloudAcademy.