I try to create a self-defined Action. The action is to play a sound from an array. Even though I managed to make it sound, I received the error saying TypeError: n.apply(...) is undefined.

The Action is called with a syntax like so:

playoneshot bird or playoneshot lion

When it is defined in the script, the idea is so that the Action play a short sound that is chosen randomly from an array of sounds. There are two arrays: one array for bird sounds, one for lion sounds. The sounds are saved into the music asset folder, and defined as assets in the script:

monogatari.assets("music", {
    "b01": "bird01.mp3",
    "b02": "sound02.mp3",
    "l01": "lion01.mp3",
    "l02": "lion02.mp3"
})

Then I defined the Action in the main.js inside the init function like the following:

class Playoneshot extends Monogatari.Action {
        static matchString([action]) {
            return action === "playoneshot";
            }
        
        constructor([myaction, soundType]){
            super();
            this.soundType = soundType;
            }
            
         apply() {
             let soundArr;
             switch (this.soundType) {
                 case "bird":
                     soundArr = ["b01", "b02"];
		     break;
		case "lion":
		     soundArr = ["l01", "l02"];
		     break;
		}
				
		// Play random one shot
		let idx = Math.floor(Math.random() * soundArr.length);
		let sound = soundArr[idx];
		monogatari.run("play music " + sound);
	}
	
	revert() {
        // nothing
	}
}
		
Playoneshot.id = "Playoneshot";
monogatari.registerAction(Playoneshot);

Could anyone help me to understand the error message? I thank you in advance!