fb.state Playback State Mirror

fb.state is a plain mutable state object that the SDK keeps synchronized through playback events. It is convenient for imperative UI reads and polling without issuing an API call for every update.

Properties

Property	Type	Description
volume	number	Current output volume on a linear 0-100 scale
isPlaying	boolean	true only when playback state is 'playing'; paused and stopped states are false
currentTrack	TrackInfo | null	Most recently announced now-playing track. Initially null; stopping playback does not clear it
position	number	Current playback position in seconds

Automatic Updates

fb.state listens to these events:

Event	Updated fields
playback:stateChanged	Updates isPlaying from state and updates position when present
playback:trackChanged	Replaces currentTrack and sets isPlaying = true
playback:stopped	Sets isPlaying = false and position = 0
playback:volumeChanged	Updates volume when present
playback:time	Updates position when present

Examples

Basic Reads

console.log(fb.state.isPlaying);     // true
console.log(fb.state.volume);        // 80
console.log(fb.state.position);      // 42.5
console.log(fb.state.currentTrack);  // {title, artist, album, ...}

Polling UI Updates

setInterval(() => {
    document.getElementById('playing').textContent = fb.state.isPlaying ? '▶' : '⏸';
    document.getElementById('position').textContent = Math.floor(fb.state.position) + 's';
}, 500);

Reading State from an Event Handler

// The SDK updates state before consumer handlers run for this event.
fb.on('playback:trackChanged', () => {
    const track = fb.state.currentTrack;
    if (track) document.title = `${track.title} - ${track.artist}`;
});

State semantics

fb.state is a mutable snapshot, not a Proxy or framework-reactive object. Subscribe through fb.on() for change notifications. Use APIs such as fb.player.getState() or fb.player.getPosition() when an authoritative value is required on demand.

SMP compatibility layer

fb.state tracks only these four playback fields. For the broader cached state used by the SMP compatibility layer, including playlists and configuration, use window.smp.cache; see SMP Compatibility.