Overview of what this course is, who this course is for, and what we'll be building

Course Introduction

Getting our local development environments set up with nvm

How to Setup a React Developer Environment with nvm

Intro & Dev Environment Setup

Module 1 Introduction

An introduction to APIs in web development

What is an API?

Learn the basics of REST principles and HTTP requests & responses

Okay, but what is a REST API?

What is Express? The Basics of the Node.js web framework

Learn the basics of writing Express route handlers

The Basics of Express Router - Requests and Responses

Getting Started with REST APIs & Express

Module 2 Introduction

Get your app set up in the Spotify developer dashboard

Getting Started with the Spotify Developer Dashboard

Set up nodemon to streamline our Node.js development workflow

Add nodemon to an Express App to Restart Node Automatically

Learn how OAuth works and how it will work with the Spotify API

What is OAuth and How Does it Work? [with examples]

Build out Spotify's Authorization Code OAuth flow with Express

How to Implement OAuth Flow in Express and Node.js

Authentication & Authorization with Spotify

Module 3 Introduction

Use Create React App to quickly spin up a React front end and pass OAuth tokens from server to client

How to Pass OAuth Tokens to a React App

Streamline development in a client/server architecture with Concurrently

Optimize React and Express.js code with npm concurrently

Setting Up a React Front-End

Module 4 Introduction

Learn how to use local storage to let users log in and log out

Using Local Storage to Persist Login State

Use axios to send a request to the Spotify Web API and render response data on the front end

How to Fetch Spotify API Data with Credentials with Axios

Scaffold out our app's pages with React Router

How to Setup and Scaffold React Router

Install and configure Styled Components in our React app

Beginner's Guide to Styled Components in React [with examples]

Login State & Front-End Scaffolding

Module 5 Introduction

How to Build a Login Page in React

How to Build a Profile Page in React with Spotify API Data

Build out and style the top artists & top tracks pages

How to Build a Spotify Top Artists & Top Tracks Page in React

How to Build a Spotify Playlists Page in React

Build out and style a page for each playlist and let users sort tracks by audio features

How to Build a Spotify Individual Playlist Page in React

Add a loading state for our React components

How to Build a React Loading Animation Component

Building & Styling the UI

Module 6 Introduction

Add a custom favicon and share image to our app

How to Change Your React Favicon and Social Preview Images

Deploy our app to the internet with Heroku

How to Deploy React to Heroku With a Node.js Server

Add a descriptive and helpful README to our project

How to Add a README.md File to React

Deploying to the Internet

Wrapping Up What We’ve Learned

Course Wrap Up

Have you ever been curious to see what your Spotify data looks like? How a round-up of your listening habits gets compiled every year? Or even wanted to see metadata of your favorite tracks? Luckily, Spotify makes a ton of interesting data like this accessible via the Spotify API. For example, there is data available for every users’ [top tracks and artists](https://developer.spotify.com/documentation/web-api/reference/#endpoint-get-users-top-artists-and-tracks) of all time and [audio features](https://developer.spotify.com/documentation/web-api/reference/#endpoint-get-several-audio-features) like danceability and tempo for every single track.

## Why this course

If you're interested in accessing personalized Spotify data like we mentioned above, Spotify requires your app to be authorized. And to get authorization, you'll need to implement something called OAuth. This course will walk you through every step of the OAuth flow in a concise, easy to follow way. Unlike YouTube tutorials that only cover a few concepts and leave you with half-baked GitHub repositories, we'll cover everything from explaining what REST APIs are to implementing Spotify's OAuth flow to fetching data from the Spotify API in React hooks. Split into seven modules, each lesson includes clear, detailed explanations and complete code examples. By the end of the course, you'll have an app deployed to the internet that you can share with your friends and add to your portfolio.

## What we’ll build

**On the front end**, we’ll build out a professional, responsive user interface with [React](https://reactjs.org/), React Hooks, and the popular CSS-in-JS library, [Styled Components](https://styled-components.com/). We’ll pull in data from the Spotify API using modern ES6 [async/await](https://developer.mozilla.org/en-US/docs/Learn/JavaScript/Asynchronous/Async_await) methods and display that data in an engaging way.

**On the back end**, we’ll learn the basics of [REST APIs](https://en.wikipedia.org/wiki/Representational_state_transfer), [HTTP requests](https://developer.mozilla.org/en-US/docs/Web/HTTP/Methods), and [OAuth](https://oauth.net/). We'll lift the veil on how to [authorize an app with Spotify](https://developer.spotify.com/documentation/general/guides/authorization-guide/), and then build a Node server with the [Express framework](https://expressjs.com/) to handle our authentication requests. Finally, we’ll deploy our app to the internet using [Heroku](https://www.heroku.com/).

![Top Artists](https://d2uusema5elisf.cloudfront.net/courses/build-a-spotify-connected-app/module_00/lesson_00.00/public/assets/screenshot-1.png)

![Top Tracks](https://d2uusema5elisf.cloudfront.net/courses/build-a-spotify-connected-app/module_00/lesson_00.00/public/assets/screenshot-2.png)

![Playlist tracks sorted by tempo](https://d2uusema5elisf.cloudfront.net/courses/build-a-spotify-connected-app/module_00/lesson_00.00/public/assets/screenshot-3.png)

Learn how to build a full stack web app to visualize personalized Spotify data with the help of Node.js, React, Styled Components, and the Spotify Web API.

Build a Spotify Connected App

Principles of REST APIs and how they relate to the Spotify API

How to implement the Spotify OAuth flow with JavaScript

How to use local storage to store auth tokens

How to fetch data from the Spotify API in a React app

How to handle async code with React hooks and async/await

How to efficiently style an app with Styled Components

How to deploy an app with a React front-end and Node.js back-end to Heroku

Since we're now running two apps simultaneously (the front end React app and the back end Express app), we have two 

 files. This means that to have our front end and back end up and running we need to make sure we've run 

 directory. In this lesson, we'll go over a few things we can do to optimize our development workflow with this setup.

What if we wanted to make an HTTP request from our React app to one of our Express app's endpoints? A good example would be when our access token expires, and we need to get a new one with the 

. Usually, when you encounter CORS errors, it's because you are trying to access resources from another domain (i.e. 

), and the domain you're requesting resources from is not permitted.

To tell the development server to proxy any unknown requests to our API server in development, we can simply set up a 

Now, if we set up a request to our Express app's 

, we should see some JSON data in addition to the tokens printed in our console.

  useEffect(() => {
    const queryString = window.location.search;
    const urlParams = new URLSearchParams(queryString);
    const accessToken = urlParams.get('access_token');
    const refreshToken = urlParams.get('refresh_token');

    console.log(accessToken);
    console.log(refreshToken);

    if (refreshToken) {
      fetch(`/refresh_token?refresh_token=${refreshToken}`)
        .then(res => res.json())
        .then(data => console.log(data))
        .catch(err => console.error(err));
    }
  }, []);

Another improvement we can make to our development workflow is adding a build tool to let us run multiple npm commands at the same time. To do this, we'll add an npm package called 

---
title: Optimize React and Express.js code with npm concurrently
description: Streamline development in a client/server architecture with Concurrently
privateVideoUrl: https://fullstack.wistia.com/medias/pyy9pathor
isPublicLesson: true
code: https://gitlab.com/fullstackio/books/newline-course-apps/brittany-chiang-build-a-spotify-connected-app-app/-/tree/main/code/module_04/lesson_04.02/protected/src?ref_type=heads
---

Since we're now running two apps simultaneously (the front end React app and the back end Express app), we have two `package.json` files. This means that to have our front end and back end up and running we need to make sure we've run `npm install` and `npm start` in _both_ the root of the project _and_ in the `client` directory. In this lesson, we'll go over a few things we can do to optimize our development workflow with this setup.

## Proxying API requests

What if we wanted to make an HTTP request from our React app to one of our Express app's endpoints? A good example would be when our access token expires, and we need to get a new one with the `/refresh_token` endpoint we set up.

If we tried to send a GET request to `http://localhost:8888/refresh_token` from `http://localhost:3000`, we would run into CORS issues.

![CORS error](https://d2uusema5elisf.cloudfront.net/courses/build-a-spotify-connected-app/module_04/lesson_04.02/public/assets/cors-error.png)

CORS stands for [Cross-Origin Resource Sharing](https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS). Usually, when you encounter CORS errors, it's because you are trying to access resources from another domain (i.e. <http://localhost:3000> and <http://localhost:8888>), and the domain you're requesting resources from is not permitted.

To tell the development server to proxy any unknown requests to our API server in development, we can simply set up a [proxy](https://create-react-app.dev/docs/proxying-api-requests-in-development/) in our React app's `package.json` file. In `client/package.json`, let's add a proxy for <http://localhost:8888> (where our Express app runs).

```json { actualFilename=./protected/src/client/package.json endLine=5 startLine=5 statedFilename=client/package.json url=https&#x3A;//gitlab.com/fullstackio/books/build-a-spotify-connected-app/module_04/lesson_04.02/protected/src/client/package.json#L5 }
  "proxy": "http://localhost:8888",
```

Now, if we set up a request to our Express app's `/refresh_token` endpoint (without the `http://localhost:8888`) using [`fetch()`](https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API/Using_Fetch) in our `App.js`, we should see some JSON data in addition to the tokens printed in our console.

```js { actualFilename=./protected/src/client/App.js endLine=21 startLine=6 statedFilename=client/src/App.js url=https&#x3A;//gitlab.com/fullstackio/books/build-a-spotify-connected-app/module_04/lesson_04.02/protected/src/client/App.js#L6 }
  useEffect(() => {
    const queryString = window.location.search;
    const urlParams = new URLSearchParams(queryString);
    const accessToken = urlParams.get('access_token');
    const refreshToken = urlParams.get('refresh_token');

    console.log(accessToken);
    console.log(refreshToken);

    if (refreshToken) {
      fetch(`/refresh_token?refresh_token=${refreshToken}`)
        .then(res => res.json())
        .then(data => console.log(data))
        .catch(err => console.error(err));
    }
  }, []);
```

## Running two servers at the same time