APIs with Fetch and Axios

Learning Objectives

After this lesson, you will be able to:

  • Create a React component that calls an API

  • Identify the pieces of a fetch() and axios() call with React.

  • Use fetch inside a React component

  • Use axios inside a React component

Introducing fetch()

So... we know what an API is. Now what?

How can we use an API to dynamically manipulate the DOM with the given data? We can use fetch().

In the past, these have been called AJAX requests. As you'll come to learn, fetch() allows us to build single page applications that do not require refreshes.

AJAX, which stands for "Asynchronous Javascript and XML," is the method through which we are able to make HTTP requests. The standard requests we will be making are GET POST PUT PATCH and DELETE.

Type of Request

What's It Do?

GET

Read ('give me movie names from your database')

POST

Create ('here's a new movie for your database')

PATCH

Update ('hey, this movie has a new title'))

PUT

Update ('hey, this movie totally changed')

DELETE

Delete ('that movie is so bad you should just take it out of the database')

The browser packages this together using fetch() and sends it off to a server. The server then listens to your request and provides a response. It looks something like this:

When you browse to your favorite websites, your browser is making a request and the server is providing a response. fetch() allows us to perform the same type of requests over a network. Imagine fetching weather information and rendering it on your website. You can use fetch() to build these applications.

Taking a look at fetch in action

That was a lot! Let's take a look at fetch() in action.

Imagine we want to fetch() the number of astronauts currently aboard the International Space Station (ISS). Good thing there is an API for that, right? This API allows us get the information using the following URL:

http://api.open-notify.org/astros.json

The API provides a response that looks like the following:

{
    "number": 5,
    "people": [
        {"craft": "ISS", "name": "Oleg Novitskiy"},
        {"craft": "ISS", "name": "Thomas Pesquet"},
        {"craft": "ISS", "name": "Peggy Whitson"},
        {"craft": "ISS", "name": "Fyodor Yurchikhin"},
        {"craft": "ISS", "name": "Jack Fischer"}
        ],
        "message": "success"
}

If you'd like, you can copy and paste the API URL into a browser to see this happen.

This particular API tells us the number of people currently in space on the ISS and their names. It also happily gives us "message: success" so we know it worked!

We can fetch this JSON easily using Javascript.

How? The skeleton code looks like this:

fetch(url)
  .then(function(response) {
    // Here you get the data to modify or display as you please
    })
  })
  .catch(function(err) {
    // If there is any error, you will catch it here
  })

Let's look at what we would apply this for our astronauts:

let issApi = 'http://api.open-notify.org/astros.json';
fetch(issApi)
  .then(function(response) => {
    return response.json();
  }).then(function(json) => {
    console.log('JSON from the ISS', json);
  }).catch(function(err) => {
    console.log('An error occured while parsing!', err);
  })

That's as simple as fetch is. While there are other ways to handle the response (such as html or blob), this approach makes writing requests to APIs and other network calls in Javascript easy.

Production Warning! It is important to note that while this is an ES6 standard, some browsers such as Internet Explorer do not support it; yet Edge does. You may need a polyfill for live projects. If you need a polyfill for a production project, Github's polyfill is very popular.

Codealong - Kanye West Quotes

It is time for you to build a very simple component that shows a randomly generated Kanye West Quote. We'll do this using the Kanye Rest. Before doing so, challenge yourself to a mini quiz.

Q: Which React method should API calls be made from?

useEffect(). Per the React documentation, If you need to load data from a remote endpoint, this is a good place to instantiate the network request.

Q: What does it mean to make GET request?

We are asking the server to send us data to read. To GET means to "read."

Fetching Kanye in a React Component

Let's go back to your blog project (so make sure it's running!).

You can use fetch() API directly inside of a React Component to render a quote. We'll be using the Home component, so open Home.js to edit.

The official React documentation tells developers that any network requests should be placed inside of the useEffect method.

  • Start by changing the Home component to have an empty useEffect() method.

  • Set the stage for returning a quote in the div by changing the text to be an <h1> with the text "My favorite Kanyw quote:"

Let's use axios instead!

fetch is great and all... but let's take this opportunity to test out another common library! axios is Promise based HTTP client for the browser and node.js! More detailed information can be found in their README on github.

import React, { useEffect } from 'react';
function Home () {
   useEffect(() => {
    fetch("https://api.example.com/items")
      .then(res => res.json())
      .then(
        (result) => {
          setIsLoaded(true);
          setItems(result);
        },
        // Note: it's important to handle errors here
        // instead of a catch() block so that we don't swallow
        // exceptions from actual bugs in components.
        (error) => {
          setIsLoaded(true);
          setError(error);
        }
      )
  }, [])

}


class Home extends Component {

  componentDidMount() {
      /* nothing here... yet! */
  }

  render() {
    return (
      <div>
        <h1>My favorite Kanye quote:</h1>
      </div>
    )
  }
}


export default Home

or with a functional component...

import React, {useEffect} from 'react'

const Home = () => {
   useEffect() {
      /* nothing here... yet! */
   }

   return (
      <div>
        <h1>My favorite Kanye quote:</h1>
      </div>
   )
  }

We can now tell our component to fetch a Kanye quote and then set it to our state. We do this by adding the axios.get() call inside of componentDidMount().

Calling this.setState() then triggers a re-render inside of our component.

You should have this inside your functional component...

import React, {useState, useEffect} from 'react'
import axios from 'axios'

function Home() {
   let [kanye, setKanye] = useState('')

   useEffect(() => {
    let kanyeRest = 'https://api.kanye.rest/';
    axios.get(kanyeRest)
    .then(response => {
          setKanye(response.data.quote)
        })
    .catch(err => console.log(err.message))
   }, [])

   return (
        <div>{kanye}</div>
   )
}

Let's test it out!

and one more time, as a functional component:

if (kanye) {
  return (
    <div>
      <h1>My favorite Kanye quote:</h1>
      <div>{kanye}</div>
      <p>Lo, my heart doth swoon... Such a way with words.</p>
    </div>
  );
} else {
  return (
   <div>
      <h1>My favorite Kanye quote:</h1>
      <div>Loading...</div>
   </div>
);
}

You're done! Your Home page should load a random Kanye quote!

For more information than you probably ever wanted to know about fetching data in React, these articles by Robin Weiruch make for a pretty complete resource:

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