JavaScript

Using the SoundCloud API with the JavaScript SDK

Mustaghees Butt
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This article was peer reviewed by Jamie Shields and Wern Ancheta. Thanks to all of SitePoint’s peer reviewers for making SitePoint content the best it can be!

SoundCloud has made available an API which allows developers to get almost any data they want. But its usage can be confusing, especially for beginners, because as of now the SoundCloud API documentation and the examples use different versions of the SDK (Software Development Kit).

What is the difference between the API and the SDK? Basically, the API is a collection of URLs that provide access to data from the SoundCloud servers, and the SDK is a pre-written library (or client) for querying the API. To learn more see this discussion.

In this tutorial, we will learn how to access the SoundCloud API and how to simplify the process using the SDK. We will walk though setting up the SDK and then write the JavaScript to get data, play audio and more from SoundCloud.

Getting Started

Knowing the concepts and workings of HTTP and APIs will be helpful. If you want to learn more about APIs, I recommend this short course: An Introduction to APIs. A little knowledge of asynchronous JavaScript, promises and callbacks will also help. jQuery is used in our code examples, so knowing the basics won’t hurt.

To start querying the SoundCloud API using JavaScript, we need to download the JavaScript SDK provided by SoundCloud. As mentioned earlier, there are two different versions of the SDK available.

Which Version of the SDK to Use?

The major difference between them is how they return data when an asynchronous request is made to the API. The latest version returns a Promise, while the other requires a callback function as a parameter.

One problem I noticed, is that with the version of SDK used by the documentation, there seems to be an issue with user-login functionality, as the pop-up window doesn’t close automatically.

So, for simplicity’s sake, and because it is more stable, we will use the old version in the examples throughout this tutorial. This version will require callback functions for asynchronous requests.

Using the SoundCloud API

Setup a Basic HTML Document

We will create a basic HTML page which will serve as our homepage. We will also include the SDK here, so we can make use of its functionality.

<!DOCTYPE html>
<html>
  <head>
    <title>Include SDK - Using SoundCloud API</title>
    <script src="//connect.soundcloud.com/sdk.js"></script>
  </head>
  <body></body>
</html>

Notice that we have included the SDK in our page directly from SoundCloud’s servers. You can also download the SDK and reference to it like:

<script src="sdk.js"></script>

To test if the SDK gets loaded in your webpage correctly:

  • Open up the page in a browser (Chrome recommended).
  • Open up Developer Console in the browser (Ctrl + Shift + J, in Chrome).
  • In the Console, type SC and press enter. SC is a Javascript Object created by the SDK which we just included.

If an undefined error shows up then it is not loading correctly. Try refreshing and make sure the path to the SDK file (sdk.js) is correct.

Register a SoundCloud App

To register a SoundCloud app, all you need is a SoundCloud account. If you don’t have one already, go ahead and create one. By registering an app, SoundCloud servers will be able to verify our request, so no one else can make a request on our behalf.

Note: We can skip this step, if we are not going to use the user-login feature in our website. It will be explained in the next section.

  • Open the SoundCloud apps page. Here any apps we have already created will be listed. Make sure you are logged in to your SoundCloud account. Note: You do not need to make a separate account for this purpose. You can use the same account which you use for personal purposes.

  • Click on the Register a new application button.
    Screenshot of the SoundCloud application dashboard

  • Give it a name and accept SoundCloud’s Developer Policies by checking the checkbox.
    Screenshot of choosing a name for the SoundCloud App

  • Click on the big Register button, to complete the app registration.

After we have successfully registered, we will be redirected to the settings page of our newly created app. There we will find our app’s Client ID, which will be used to authorize our requests. We can leave the website and callback fields for now. We’ll get to that later.

Initialize the Client

By “initializing the client”, we mean to make the client ready to exchange data between itself and SoundCloud API. We can do it in our basic HTML document, which we created earlier, or in an external .js file.

The JavaScript syntax to do so is:

SC.initialize({
  client_id: "CLIENT_ID",
  redirect_uri: "CALLBACK_URL"
});

Let’s break it down:

  • The CLIENT_ID is provided to us when we register our app.
  • CALLBACK_URL is the URL to callback.html, an HTML file which gets called after the user has logged in. We will create it soon.

Now, after initialization, we are ready to query the SoundCloud API. Let’s take a look at some examples of what we can do already.

Examples

If we open up browser console and type SC., a list of methods associated with the SC object will appear. SC.get(uri, callback) is one of them, which is used for making GET requests to the API.

Getting a List of Tracks

To get a list of random tracks, we can use SC.get() like this:

SC.get("/tracks", function(response) {
  for (var i = 0; i < response.length; i++) {
    $("ul").append("<li>" + response[i].title + "</li>");
  }
});

See the Pen Listing Tracks by SitePoint (@SitePoint) on CodePen.

What this does, is that it queries the /tracks endpoint and expects a callback function. The response is stored in the response parameter of callback, which is an array of JavaScript objects with multiple properties, title being one of them. We can console.log(response[0]) instead of looping to see a whole object and its properties. Then we will know which properties we have access to.

Notice, in this example we have not specified a callback URL during initialization. This is because here it doesn’t matter if we specify it or not. Either way our code will work. But when we will implement user-login functionality, it will matter and will be required so no one else can use our Client ID.

Embedding a Track

The SC object offers another method, SC.oEmbed(url, options, callback), which embeds the SoundCloud player in our website and allows us to play a track of our choice.

SC.oEmbed('https://soundcloud.com/username/complete-url-to-the-track', {maxheight: 200, auto_play: false}, function(res) {
  $("#player").html(res.html);
});

See the Pen Embedding a Track by SitePoint (@SitePoint) on CodePen.

Let’s break it down:

  • First we give it a complete URL of the track we want to play.
  • In the options parameter, we set some options for the player. See more here.
  • In the callback function, we replace the contents of an element (#player) in our page with the HTML code for the player (res.html).

This trick can be used to embed a song or music in a website.

Implementing User Login

For the implementation of user-login functionality, we need to have a callback URL for authorization purposes. This is a requirement of the OAuth protocol. If you are curious about it, here’s a simplified explanation of : OAuth 2 Simplified. So let’s go ahead and update the app settings to include a callback URL of callback.html, which we are now going to create.

Create the Callback Page

After a user has logged in, the pop-up window redirects to this file. In our case, we will name it callback.html and it will reside in the same directory as our home page (index.html). This is the file we need to give in the callback field in our app settings.

Screenshot of setting the redirect URL

The code we need to use within the callback file is provided in documentation. However, the documentation is a little outdated, so we’ll modify it slightly to meet modern standards.

You can modify its message and design as much as you would like to , but for now, we will keep it as simple as possible:

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
    <title>Connect with SoundCloud</title>
  </head>
  <body>
    <h4>This popup should automatically close in a few seconds</h4>

    <script>
      document.onload = function () {
        window.opener.setTimeout(window.opener.SC.connectCallback, 1);
      }
    </script>
  </body>
</html>

Logging the User In

SC.connect(callback) is the method for implementing the user-login feature. It opens up a pop-up window, prompting the user to login to their SoundCloud account. The basic usage is as below:

SC.connect(function () {
  console.log("User has logged in");
});

A slightly more interesting example would be:

SC.connect(function () {
  SC.get("/me", function (response) {
    console.log("Welcome" + response.username);
  });
});

Let’s break it down:

  • After the user has logged in, they will be redirected to callback.html, which we created earlier.
  • Then the pop-up window will automatically close, as we can guess by reading the code in callback.html.
  • After that, our callback function will get called, in which a GET request to /me endpoint is made using SC.get() method.
  • As soon as the GET request completes, its callback function gets executed and a welcome message gets logged to the console.

Notice that a request to /me will return data about the currently logged in user. Therefore, using it before the user has been logged in will result in an error message.

Playing with the User’s Data

Once the user has logged in, there is so much more we can do. To demonstrate some of the power, I have created a demo website on GitHub. You can find the source code here and see it in action here.

Let’s walk through two of the files. In index.html, the four divs are of importance, as they get filled out with user data after user has logged in:

<main>

    <div id="ui">
        <h2>Welcome <span></span></h2>
        <img id="avatar" />
        <div id="description"></div>
    </div>

    <!-- TRACKS -->
    <div id="tracklist">
        <h3>Your Tracks:</h3>
        <ul></ul>
    </div>
    <!-- PLAYLISTS -->
    <div id="playlists">
        <h3>Your Playlists:</h3>
        <ul></ul>
    </div>

    <div id="player"></div>

</main>

The next most important file is script.js: all of the magic happens here. Most of the code will be familiar to us, but let’s walk through it quickly:

// Initialization of SDK
SC.initialize({
  client_id: "21832d295e3463208d2ed0371ae08791",
  redirect_uri: "http://mustagheesbutt.github.io/SC_API/callback.html"
});
  • First we initialize our app. Notice, this time we have redirect_uri specified as our callback.html page. This URL or URI should exactly match with the URL we have specified in our app settings.
// Login handler
var user_perma;
$("#login").click(function () {
    SC.connect(function () {
        SC.get("/me", function (me) {
            user_perma = me.permalink;
            setUI(me.username, me.avatar_url, me.description);
        });
        if (SC.isConnected) {
            $("header, main").addClass("loggedIn");
        }
        getTracks();
        getPlaylists();
    });
});
  • Then we attach a click event handler to the #login button. Which when clicked, will execute SC.connect(callback) which opens a pop-up window prompting user to login.
  • After the user has logged-in, pop-up window closes. Then the callback function of SC.connect() gets executed. Inside the callback function, we make a GET request to the /me endpoint which returns the object of currently logged-in user. In the callback of the GET request we just made, we store the user’s permalink in the variable user_perma, which is defined in global scope, so we can use it later.
  • The functions setUI(), getTracks() and getPlaylists(), set up the UI, list the user’s tracks and list the user’s playlists respectively. These functions are defined in the same file.
// play something
function play(uri) {
    url = "http://soundcloud.com/" + user_perma + "/" + uri;
    SC.oEmbed(url, {maxheight: 200}, function (resp) {
        $("#player").html(resp.html);
    });
}

// when a track or playlist gets clicked, play it using `play()` function
$("ul").on("click", function (e) {
    var title = e.target.innerHTML;
    if ( tracks.hasOwnProperty(title) ) {
        play(tracks[title]);
    } else if (playlists.hasOwnProperty(title)) {
        play("sets/" + playlists[title]);
    }
});
  • When any track or playlist name gets clicked, the play() function executes, which embeds an audio player in our page using the SC.oEmbed() method, for that track or playlist .

There is much more we can do, such as getting or updating the user’s description, getting the user’s avatar, seeing who the user is following and their favourites.

Summary

  • Use the older version of the SDK, if user-login feature is to be used. It is stable, and data is returned using callback functions.
  • If the user-login feature is not used, the newer version of the SDK can be used. It uses promises to return data.
  • Data from SoundCloud API can be accessed by a simple GET request.
  • User-specific data can be obtained using /me endpoint, but only if the user is logged-in to our website using their SoundCloud account.

Querying an API from the client-side is a powerful tool as it saves us from the complexities of back-end. The SDK makes our lives a whole lot easier. After learning its basics, we can create even more powerful and user-friendly web applications. See some examples of what’s possible, and check out the official SoundCloud documentation to learn more about the advanced API methods available.

I’d love to hear from you about what things you’ve built (or are planning to build) with the SoundCloud SDK. Let me know in the comments!