Previous chapters have asked for a Node.js runtime. In this chapter, we will take a look at how we can get this installed on our system. If we head over to https://Node.js.org/en/, we will be able to download either the Long-Term Support (LTS) version or the current version. For this book, it is recommended to get the current version as the module support is better.

For Windows, all we need to do is download and run the executable. For OS X and Linux, this should also be simple. For Linux users especially, there may be a version in the repository manager for a specific distribution, but this version may be old or line up with the LTS version. Remember: we want to be running the latest version of Node.js.

Once we have it installed, we should be able to invoke the node command from any command line (Linux users may have to invoke the Node.js command since some repositories already had a node package inside of their repository). Once invoked, we should be greeted with a Read Evaluate Print Loop (REPL) tool. This gives us the ability to test out some code before we actually write it into a file. Run the following fragments of code:

1 + 2 //3
typeof("this") //'string'
const x = 'what' //undefined
x //'what'
x = 'this' //TypeError: Assignment to a constant variable
const fun = function() { console.log(x); } //undefined
fun() //'what' then undefined
fun = 'something' //TypeError: Assignment to a constant variable

From these examples, it should be obvious that we are working in a similar environment to the one we are used to in the browser. We have access to most of the data manipulation and functional concepts that we had in the browser.

Many of the libraries/APIs that we do not have access to are ones that are specific to the browser, such as the DOM APIs. We also don't have access to any of the browser external resource access libraries, such as Fetch or XMLHttpRequest. We have lower-level versions of them that we will talk about later, but it should be noted that, in some ways, it isn't as simple as calling the fetch API.

Go ahead and play with the REPL system. If we want to come out of it, we just need to use Ctrl + C twice on Windows (Linux should be the same; for OS X, we need to use command + C). Now, to run a script, all we need to do is put some code in a JavaScript file and call node <filename>. This should run our script in immediate mode. This can be seen in the following example.js file:

const x = 'what';
console.log('this is the value of x', x); //'this is the value of x what'
const obj = {
    what : 'that',
    huh : 'this',
    eh : 'yeah'
}
console.log(obj); // { what : 'that', huh : 'this', eh : 'yeah' }

To get access to the various built-in libraries that Node.js gives us, we can utilize two different methods. First, we can use the old require system. The following script shows this capability:

const os = require('os');

console.log(os.arch()); //prints out x64 on 64-bit OS
console.log(os.cpus()); //prints out information on our CPU

This is the current way of bringing in built-in/user-built modules. It was the style that the Node team decided on since there was no common way of bringing in modules. We had systems such as RequireJS or CommonJS, and Node.js decided on the CommonJS style of bringing in modules. However, as we have learned, there is also a standardized way of bringing modules into the browser. The same is true for the Node.js platform.

import os from 'os';

console.log(os.arch());
console.log(os.cpus());

We will also need to have a package.json file that has "type" : "module" in its manifest.