How to Chain Method Calls in Howler.js

Chaining method calls in howler.js is an efficient way to trigger multiple audio operations sequentially on a single Howl instance. By returning the library’s instance after executing a command, howler.js allows you to write cleaner, more readable JavaScript code. This article demonstrates how to implement method chaining with practical examples and explains the rules for which methods can be chained.

How Method Chaining Works in Howler.js

In howler.js, most setter methods (methods that change a state or trigger an action) return the Howl instance itself. Because the returned value is the original object, you can immediately append another method call to the end of the statement.

Here is a basic example of chaining the volume() and play() methods:

// Initialize the Howl instance
const sound = new Howl({
  src: ['audio.mp3']
});

// Chain volume adjustment and play execution
sound.volume(0.5).play();

In this example, volume(0.5) sets the audio level to 50% and returns the sound instance, allowing .play() to be called immediately afterward.

Advanced Chaining Examples

You can chain multiple operations together to create complex audio behaviors in a single block of code. For instance, you can adjust the playback rate, set a fade effect, and play the audio simultaneously:

sound.rate(1.2)
     .fade(0, 1, 2000)
     .play();

This chain increases the playback speed by 20%, fades the volume from 0 to 1 over two seconds, and starts playing the track.

Limitations: Getters vs. Setters

While most howler.js methods support chaining, you cannot chain methods after calling a “getter” method. Getter methods retrieve information from the Howl instance rather than modifying it.

Because getters return specific values (such as a number, a string, or a boolean) instead of the Howl instance, the chain will break.

// This works because volume(0.8) is a setter
sound.volume(0.8).play(); 

// This will throw an error because volume() as a getter returns a number, not the Howl instance
const currentVolume = sound.volume().play(); 

To keep your code functional, ensure that any method used in a chain is acting as a setter or an action. If you need to retrieve a value, do so in a separate, dedicated line of code.