# Installing the Express Server (backend)

**Outline**
  * [What is Express?](#what-is-express)
  * [Installing the Express Server](#installing-the-express-server)
  * [Starting the Express Server](#starting-the-express-server)
  * [Debugging](#debugging)

## What is Express?
[Express](https://expressjs.com/) is a backend web application framework for Node.

We will use Express to create custom endpoints that our frontend React App can make calls to. When we make requests to these custom endpoints, the Express server will make REST API calls to our desired 3rd party service endpoint, receive the response, and then route the response back to our frontend React App.

## Installing the Express Server
(1) From your terminal, go to your **myproject** folder

  ```bash
  cd .../myproject
  ```

(2) Create **backend** folder

  ```bash
  mkdir backend

  cd backend
  ```

(3) Create your Express project

  ```bash
  npm init
  ```

  * Hit enter to skip the questions

(4) Continue to install some dependencies

  ```bash
  npm install express node-fetch cors
  ```


(5) Create a **server.js** file inside the **backend** folder

  ```bash
  touch server.js
  ```

## Starting the Express Server
(1) Configure the **server.js** file

(2) From your terminal, go to your **backend** folder

  ```bash
  cd .../myproject/backend
  ```

(3) Start the Express Server

 ```bash
  node server.js
  ```

---

## Debugging

No response when starting the Express server?
  * Make sure you are inside the `backend` folder when starting the Express server

Got a `UnhandledPromiseRejectionWarning` error?

```text
(node:5379) UnhandledPromiseRejectionWarning: FetchError: request to https://.kintone.com/k/v1/records.json?app= failed, reason: getaddrinfo ENOTFOUND .kintone.com
```

  * Looks like Kintone API credentials are missing
  * Be sure to enter your Subdomain, App ID, and API Token under the `Kintone API Setup` section in `server.js`

Got a `GAIA_IA02` error?
  * Enter the App's API Token in `apiToken`
  * Be sure to hit the `save` button & the `Update App` button to implement the API Token change.