Imports (part 3)

2020-08-23 Articles Renso Diaz

When it comes to developing a web application with Node.js Imports play a very important role in the creation of our application. They help us to structure and restructure the application any way that we want. But also gave us the ability to use modules written by other people and integrate them into our application.

In Fact you already did create one and use it. In our Part 2 lesson when we created environment variables. If you don’t remember you can always go back to read the article.

One thing to get clear is that imports are strictly read only, no modification is allow out of the scope of the module that exports it. If you need to modify the module that you are importing you will have to go inside that specific file and make the changes.

Now let’s see an import using Javascript and then we will see how does it change when using a framework like Express:

import myModule from "path/to/module-name";

Beside the import and from statements in the above code block there are two things that can make our code more readable:

myModule: Name of how you would like to identify your module in the current scope.
module-name: The actual name and location of your module.

Imports in Express.js are a bit different in syntax but the core function on how they operate are very similar to the example above.

const config = require('./config');

As you can see we use a variable type const, if you have been following along you will remember what we said about import been strictly read only const are variables that won’t change after a declaration and value have been assigned to them.

Exports

We have been talking about Imports but there is another important part that comes hand in hand when are creating modules and using them anywhere else in your code, that is call Exports.

To start with Exports let’s use the module we created in Part 2 called Config.js

module.exports = {
   ENV: process.env.NODE_ENV || 'development',
   PORT: process.env.PORT || 4040
}

You can also use variables and obtain the same result like this:

Const config = {
   ENV: process.env.NODE_ENV || 'development',
   PORT: process.env.PORT || 4040
}
module.exports = config

A one thing to noticed from the code above is module.exports we are letting the parent scope of our application that we have a module and that we would like to use it somewhere else in our application.

In our next lesson we will talk about NPM modules, we will see how to install and delete them. also we will see how we can import them into our application.