Modules

Modules provide a way to encapsulate your code and create privacy. In object-oriented languages, we usually use classes for this. However, I actually believe that this is an anti-pattern rather than a good practice. Classes should be used where inheritance is desired and not just to structure your code.

I'm sure that you've encountered a lot of different module patterns in JavaScript already. One of the most popular ones that creates privacy using a function closure of an immediately invoked function expression (IIFE) is probably the revealing module pattern. If you'd like to read more about this and maybe other great patterns, I recommend the book Learning JavaScript Design Patterns, by Addy Osmani.

Within ECMAScript 6, we can now use modules to serve this purpose. We simply create one file per module, and then we use the import and export keywords to connect our modules together.

Within the ECMAScript 6 module specification, we can actually export as many things as we like from each module. We can then import these named exports from any other module. We can have one default export per module, which is especially easy to import. Default exports don't need to be named, and we don't need to know their name when importing them:

import SomeModule from './some-module.js'; 
var something = SomeModule.doSomething(); 
export default something; 

There are many combinations on how to use modules. We will discover some of these together while working on our task management application during the upcoming chapters. If you'd like to see more examples on how to use modules, I can recommend the Mozilla Developer Network documentation (https://developer.mozilla.org) on the import and export keywords.