A base class compatible with the Web API 'SpeechRecognition' spec.

speech-recognition-base.js

/**
 * A base class compatible with the Web API 'SpeechRecognition' spec.
 *
 * @author NDF, 13-Oct-2020.
 * @see https://developer.mozilla.org/en-US/docs/Web/API/SpeechRecognition
 */

const Event = window.Event;
const EventTarget = window.EventTarget;
export const SpeechRecognition = window.SpeechRecognition || window.webkitSpeechRecognition;
export const SpeechRecognitionEvent = window.SpeechRecognitionEvent || window.webkitSpeechRecognitionEvent;
export const SpeechGrammarList = window.SpeechGrammarList || window.webkitSpeechGrammarList;

export const SPEECH_RECOGNITION_EVENTS =
'audioend,audiostart,end,error,nomatch,result,soundend,soundstart,speechend,speechstart,start'.split(',');

export /* abstract / interface */ class SpeechRecognitionBase extends EventTarget {
  constructor () {
    super(...arguments);

    this.continuous = false;
    this.grammars = new SpeechGrammarList(); // {length: 0}
    this.interimResults = false;
    this.lang = '';
    this.maxAlternatives = 1;

    this._eventHandlers();

    // console.debug(this.constructor.name, this);
  }

  _notImplemented (label) {
    console.warn(`SpeechRecognitionBase. Not implemented: '${label}()'`);
  }

  _eventHandlers () {
    SPEECH_RECOGNITION_EVENTS.forEach(evName => {
      const onEvent = `on${evName}`;
      this[onEvent] = (ev) => this._notImplemented(onEvent);
    });
  }

  // EventTarget.
  addEventListener (evName) { this._notImplemented(`addEventListener (${evName})`); }

  abort () { this._notImplemented('abort'); }
  start () { this._notImplemented('start'); }
  stop () { this._notImplemented('stop'); }
}

export class SpeechRecognitionEventBase extends Event {
  constructor () {
    super(...arguments);

    this.emma = null; // Readonly; XML; Obsolete.
    this.interpretation = null; // Readonly; Obsolete.
    this.resultIndex = 0;
    this.results = null; // { length: 0 }; // SpeechRecognitionResultList.
  }
}

// export const speechRecognitionBase = new SpeechRecognitionBase();