This course will be retired on August 10, 2021. We recommend "REST APIs with Express" for up-to-date content.

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Create an Express App

5:52 with Andrew Chalkley and Joel Kraft

Often when starting an Express project, it makes sense to use express-generator to create a starting place for us. But for our purposes this would create a lot of unnecessary files we would have to then delete. That’s because express-generator builds in a lot of user interface-based files like templates and static files (HTML, CSS or client-side JS), which REST services have nothing to do with, being solely data-based. We’ll instead work the other way, and create our app from scratch, which it turns out is not actually too hard to do! Let’s get started.

It's time to start coding. 0:04
If you've used express in a project before, 0:06
you may have used express Generator to create boilerplate code. 0:09
express generates or provides starter code to set static HTML, CSS and image files. 0:14
Since our API will only send JSON, 0:20
the extra express generated code isn't required. 0:23
It's easier for us to start from scratch. 0:27
To build our API, we'll be using a command line terminal and a text editor. 0:30
It doesn't matter which text editor you use, but I'll be using sublime text. 0:36
Let's start a terminal window. 0:43
If you haven't created a folder where you want to build this project, 0:46
create that now. 0:50
It doesn't matter what you call it. 0:51
I'm going to call mine qa-rest-api. 0:54
Change into that directory and run npm 1:02
init --yes. 1:07
This accepts all defaults and creates the package.json. 1:11
It's a fast way to create a basic package.json file. 1:17
Thoughtful configuration of a package.json file is usually a great idea, 1:21
and there's a Treehouse course on using MPM that covers this in depth. 1:26
But for our purposes this default configuration will be fine. 1:31
Next, let's install express by 1:37
running npm install express@ tilde, 1:42
which means any patch release, 1:48
4.13-- save. 1:54
Once express is installed, switch over to your text editor and 2:05
create a new file, app.js. 2:09
This will be our apps main file. 2:24
Let's adjust the package.json file to reflect that. 2:27
At the top of the app.js file we will type use strict, 2:36
to help us write better code. 2:42
If you'd like to know more about this, Treehouse has a workshop 2:49
on this statement, you can find the link in the teacher's notes below. 2:52
Then we'll bring in the express 2:56
module with var express is 3:02
equal to require express. 3:07
Let's use the express function to return an instance of our application. 3:12
We can store this in the variable app. 3:18
The application object is stored in the app variable. 3:27
This will let just control how the application behaves, 3:31
when restful requests are made to it. 3:34
We'll configure it shortly. 3:36
Right now, let's add a couple more lines, to get our app into a working state. 3:39
First, we'll need to specify a port to serve the app on. 3:45
Var port is equal to 3:50
process.env.PORT or 3:55
3000. 4:00
This expression will evaluate to 3000 unless we're deploying the out to 4:03
a production environment. 4:07
We won't need to worry about any of this in this course, though. 4:09
For our purposes, this will set the port to 3000. 4:13
We can start the server by calling app.listen, and 4:17
passing in the port to listen on. 4:20
If we started the app now, it would work. 4:29
But you wouldn't be able to see anything in the browser. 4:33
We haven't set up any routes. 4:37
You'd only know the sever was running, 4:40
because there'd be no error in the console. 4:42
Let's give ourselves some feedback. 4:46
App.listen also accepts a call back function as its second parameter, 4:48
which will be called once the server has begun to listen for requests. 4:53
Let's provide a callback that will lock some text to the console once the server 5:08
has successfully set up. 5:13
Express server is listening on port and 5:17
then the port variable. 5:24
Let's save this file and switch back to the terminal to start the app. 5:31
There is the message, letting us know that the server is active, 5:39
not much to see yet but it's a good start. 5:44
We'll build the Express app up in the next video. 5:48

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