A plain JavaScript to connect to the API using HTTP requests

API stands for Application Program Interface, which can be defined as a set of methods of communication between various software components. In other words, an API allows software to communicate with another software.

We'll be focusing specifically on Web APIs, which allow a web server to interact with third-party software. In this case, the web server is using HTTP requests to communicate to a publicly available URL endpoint containing JSON data. If this is confusing now, it will make sense by the end of the article.

You may be familiar with the concept of a CRUD app, which stands for Create, Read, Update, Delete. Any programming language can be used to make a CRUD app with various methods. A web API uses HTTP requests that correspond to the CRUD verbs.

If you've heard REST and RESTful APIs, that is simply referring to a set of standards that conform to a specific architectural style. Most web apps do, or aim to conform to REST standards. Overall, there are a lot of terms, acronyms and concepts to understand - HTTP, API, REST - so it's normal to feel confused and frustrated, especially when API documentation assumes you already know what to do.

Let's take a look at the Studio Ghibli API documentation. This API was created to help developers learn how to interact with resources using HTTP requests. Since an API can be accessed by many different methods - JavaScript, PHP, Ruby, Python and so on - the documentation for most APIs doesn't tend to give specific instructions for how to connect.

Before we try to put anything on the front end of the website, let's open a connection the API. We'll do so using XMLHttpRequest objects, which is a way to open files and make an HTTP request.

We'll create a request variable and assign a new XMLHttpRequest object to it. Then we'll open a new connection with the open() method - in the arguments we'll specify the type of request as GET as well as the URL of the API endpoint. The request completes and we can access the data inside the onload function. When we're done, we'll send the request.

// Create a request variable and assign a new XMLHttpRequest object to it.
var request = new XMLHttpRequest()

// Open a new connection, using the GET request on the URL endpoint
request.open('GET', 'https://ghibliapi.herokuapp.com/films', true)

request.onload = function() {
  // Begin accessing JSON data here
}

// Send request
request.send()

Now we've received a response from our HTTP request, and we can work with it. However, the response is in JSON, and we need to convert that JSON in to JavaScript objects in order to work with it.

We're going to use JSON.parse() to parse the response, and create a data variable that contains all the JSON as an array of JavaScript objects. Using forEach(), we'll console log out the title of each film to ensure it's working properly.

// Begin accessing JSON data here
var data = JSON.parse(this.response)

data.forEach(movie => {
  // Log each movie's title
  console.log(movie.title)
})

Using Inspect on index.html and viewing the console, you should see the titles of 20 Ghibli films. Success!