Notes

Node Refresher

Edit on GitHub

Node API
4 minutes

Nodejs

  • Nodejs is simply a way to run JavaScript outside the context of the browser. Powered by V8.
  • Most of the browser APIs do not exist in Node (no document object etc.) Some are still there, like console (tip: type console in Node REPL to see available methods)

Executing Nodejs

  • You can use the REPL
1node
2>
  • You can execute files
1node file.js

NPM

  • NPM is a package manager to handle dependencies. Using the package.json to store meta info about your package and what packages it may need.
  • NPM is the standard, comes builtin with Nodejs
  • All 3rd party modules, when downloaded, will be placed in the node_modules directory by default
  • The node_modules/ folder will always be at the root of the application, thanks to npm

CommonJS

  • Node uses CommonJS for it’s module loader. Using require() we can get access to built in and 3rd party modules
  • In HTML files you have <script> tags, in Nodejs JavaScript you use require() to associate with other JavaScript files/modules (aka a Module Loader)
1// built in Node module
2var path = require('path'); // no ./ prefix means Node will assume it's either builtin or the a module in the default location (node_modules/)
3
4// 3rd party module downloaded in node_modules/
5var _ = require('lodash');
6
7// a module we created in another file
8var myModule = require('./path/to/my/module'); // you have to prefix with ./
  • For builtin and downloaded (via npm) modules you don’t have to provide the directory. For custom modules, you have to prefix the path with ./
  • You don’t have to add .js at the end, it assumes it’s a JavaScript file by default. If you do put the extension, it’ll still work, but you don’t have to.

Exposing modules with CommonJS

 1// config.js
 2exports.setup = function () {}; // attach things to the `exports` object
 3exports.enable = function () {};
 4exports.ready = true;
 5
 6// otherFile.js
 7// alternate way: `module.exports` is the entire object
 8module.exports = {
 9	action: function () {};
10	trigger: true;
11}
  • Using the exports object on module we can expose our code to be required later. To execute node against a file we can run node path/to/file

exports vs. module.exports

  • Once you use module.exports you can not export anything else in that file. module.exports is the only code that’s going to be exported
  • Using exports it’ll always be an object when you require() it. So you can have exports.setup and exports.enable and exports.ready (a lot of exported stuff in your module) and
  • Using module.exports it will be whatever you export on module.exports, e.g. it can be number 5
1// config.js
2exports.setup = function () {}; // attach things to the `exports` object
3exports.enable = function () {};
4exports.ready = true;
5
6// otherFile.js
7// alternate way: `module.exports` is the entire object
8module.exports = 3

1var myModule = require('./config'); // this will be an object containing all the exported properties (exports.setup, exports.config, exports.ready)
2var myOtherModule = require('./otherFile'); // this will be whatever you exported with module.exports, in this case: 3

Globals

  • Node wraps the code you write in an IIFY (Immediately Invoked Function Expression) and passes it stuff (globals) in that function wrapper
1(function(module, exports, __dirname){ 
2	// your actual code 
3})()
  • Every file you create is wrapped in one of the above IIFY and gets passed globals. That’s how you can access module and exports and __dirname and all of that stuff in your code, because it’s attached that way.

ES6 Modules

  • ECMAScript 2015 (aka ES6) comes with it’s own Modules system. It is not yet supported out of the box (You’ll need Babel to transpile).
1export const m = 1;

1import {m} from “foo”;
Browse all topics