03apis-axios.md

APIs with Express (axios)

Objectives

• Describe the purpose of using an API on the backend.
• Create an application that uses an API and the axios module.

In order to get around issues such as CORS and API access control, we can communicate with other servers through our server. In this case, our server acts as both a client and a server. We'll be doing some requests using the axios Node module.

To use the module, install it using npm.

npm i axios

Here's an example from NPM's homepage for the axios module. Let's take a look at it.

const axios = require('axios');

// Make a request for a user with a given ID
axios.get('/user?ID=12345')
  .then(function (response) {
    // handle success
    console.log(response);
  })
  .catch(function (error) {
    // handle error
    console.log(error);
  })
  .finally(function () {
    // always executed
  });

Identify what's necessary for making a server-side request.

• axios module import
• axios.get function
  • URL
  • any other data or headers that need to be passed (optional)
  • then promise (the code that runs once the request finishes)
    • handle a success
    • catch any raised exceptions or errors (optional)
    • run something at the end regardless (optional)

Incorporating axios into Express

In order to incorporate the axios module into Express, we can set up a basic Express application and place the request code inside a route.

This can be done by creating a new directory, running npm init, then installing the correct dependencies (refer back to the notes if you forgot). Here's an example app.

Example

server.js

const express = require('express');
const axios = require('axios');
const app = express();

app.get('/', (req, res)=>{
    axios.get('http://www.google.com')
      .then(response=>{
        // handle success
        console.log(response)
      })
  })

app.listen(3000);

Take a look inside the object you get back. You'll see that the html comes back inside the data field of the object. Like fetch, axios also has a wrapper it gives us in the response. So let's modify our console.log to get back just the data we're looking for, and change it to a res.send so we see it in the browser:

app.get('/', (req, res)=>{
    axios.get('http://www.google.com')
      .then(response=>{
        // handle success
        res.send(response.data)
      })
})

Note that this app sends out the HTML for http://www.google.com, minus the images due to the images having links relative to http://localhost:3000

Let's use a more useful source of data that we can parse, like OMDB (Open Movie Database)

Fetching JSON data

Let's modify the example above to make a request to OMDB's API. OMDB Link

We'll be using this endpoint: http://www.omdbapi.com/?s=star+wars&apikey=yourkey123

Modified Example

server.js

const express = require('express');
const axios = require('axios');
const app = express();

app.get('/', (req, res)=>{
  axios.get(`http://www.omdbapi.com/?apikey=${process.env.API_KEY}&s=star+wars`)
    .then((response)=>{
        res.send(response.data)
    })
})

app.listen(3000);

API Keys

Notice that OMDB API has a key requirement for their API. That's okay, it just means we'll need to register for a key real quick before running the example. Don't worry - it's free and only takes a few minutes. Lots of APIs will require keys, so let's get into the habit!

Protip: Never share your API keys! These should go in .env files and never, ever be pushed up to Github or anywhere else online. The .env file can be added to your .gitignore file to make git ignore it!

Things to Note

• It's very important to call res.send in the correct place (the axios 'then' promise)
  • Try putting res.send outside of the 'then'. You'll get an error!

Additional Topics

• API Information
• Using APIs with Client/Secret Keys (Foreman)