Building a 'Now Playing' Feature

As part of the rebuild of this site (which I’ll write more about when things have settled) I thought it would be fun to add a feature that shows what music I’m currently listening to, or what I last listened to. The people need to know.

I mostly use Spotify, and I thought they didn't support grabbing the currently playing song from their API. Turns out they support fetching the currently playing, and recently played tracks.

I assumed it wasn’t available and jumped straight in with something I had implemented before by using Last.fm. This works from the settings in Spotify to connect it to your Last.fm account. You can sign up for an API account if you want to go this route. Make sure to make a copy of the key you’re given, as there’s no facility available to see it again once you leave that page.

Putting it all together

Here’s the plan:

• CSS custom properties are magic, and I’d like to use them to learn more about them
• JavaScript async/await for the request
• Not everyone will see this, or care about it. It should be opt-in to save on a request

CSS: More than style

I’m using CSS custom properties to display content. As far as I’m aware it can be read by screen readers, but I’m happy to be corrected on that.
The idea is to have a custom property that has an initial value of Loading...:

:root {
    --current-track: 'Loading...';
}

Then when the user triggers the request, the property will be updated with the track information, which is displayed like this:

...::after {
    content: var(--current-track);
}

So before the request has completed, you’re seeing Loading....

Here’s the CSS we need:

.c-now-playing {
  position: fixed;
  z-index: 10;
  bottom: 50px;
  right: 50px;
}

.c-now-playing__trigger {
  display: flex;
  justify-content: center;
  align-items: center;
  position: relative;
  border-radius: 50%;
  background-color: #fff;
  width: 45px;
  height: 45px;
  transition: background ease 0.3s;
}

.c-now-playing__trigger:focus {
  outline: none;
}

.c-now-playing__trigger:after {
  content: var(--current-track);
  background-color: #ff3b3f;
  color: #f3f3f3;
  font-size: .875rem;
  padding: 0.75rem;
  position: absolute;
  right: 0;
  pointer-events: none;
  border-radius: 2px;
  line-height: 1.4;
  bottom: 100%;
  width: 230px;
  opacity: 0;
  transform: translateY(-15px);
  transition: opacity ease 0.3s, transform ease 0.3s;
}

.c-now-playing__trigger:hover,
.c-now-playing__trigger:focus {
  background-color: #ff3b3f;
}

.c-now-playing__trigger:hover:after,
.c-now-playing__trigger:focus:after {
  transform: translateY(-5px);
  opacity: 1;
}

.c-now-playing__trigger:hover .c-now-playing__icon,
.c-now-playing__trigger:focus .c-now-playing__icon {
  color: #f3f3f3;
}

And the corresponding HTML:

<button type="button" class="c-now-playing__trigger js-lt-trigger">
  Now Playing
</button>

The JavaScript

The code required for this to work is minimal — we need a way to request the latest track, and update the custom property with the result.

const endpoint = 'https://ws.audioscrobbler.com/2.0/?method=user.getrecenttracks&user=NAME&api_key=API_KEY&format=json&limit=1'

export const ListeningTo = {
  hoverTrigger: document.querySelector('.js-lt-trigger'),

  init() {
    this.updateRecentTrackVariable('Loading...')

    this.hoverTrigger.addEventListener(
      'mouseenter',
      this.fetchLatestTrack.bind(this),
      { once: true }
    )
  },

  async fetchLatestTrack() {
    try {
      let { recenttracks } = await fetch(endpoint).then(res => res.json())
      let { artist, name } = recenttracks.track[0]

      this.updateRecentTrackVariable(`Currently listening to: ${name} by ${artist['#text']}`)
    } catch (e) {
      this.updateRecentTrackVariable(`Error loading track: ${e}`)
    }
  },

  updateRecentTrackVariable(value) {
    document.documentElement.style.setProperty(
      '--current-track',
      `'${value}'`
    )
  }
}

// when imported, you can call ListeningTo.init() to start.

In the init function, it only fires when the trigger is hovered, and it’ll only happen once per page load. There’s no need to keep making the request after that.

Sin é (that’s it)

You can see the result in the bottom right corner of the site, in the future I’ll probably refactor it to use the Spotify API. In the meantime, however, it works just fine.