rx.speech.js

function beginSpeechRecognition(options) {
  options = options || {};
  
  var engine = new webkitSpeechRecognition();
  
  Object.keys(options).forEach(function (key) {
    engine[key] = options[key];
  });
  
  engine.start();
  
  var failed = false;
  
  var recognitions = Rx.Observable.create(function (observer) {
    engine.addEventListener('result', function (recognition) {
      observer.onNext(recognition);
    });
    
    engine.addEventListener('error', function (err) {
      failed = true;
      observer.onError(err);
    });
    
    engine.addEventListener('end', function () {
      observer.onCompleted();
    });
  });
  
  var lifecycle = Rx.Observable.create(function (observer) {
    engine.addEventListener('start', function () {
      var alive = true;
      observer.onNext(alive);
    });
    
    engine.addEventListener('end', function () {
      var alive = false;
      observer.onNext(alive);
      observer.onCompleted();
    });
  });
  
  var phrases = recognitions.map(function (recognition) {
    var transcripts = [];
    
    for (var i = 0; i < recognition.results.length; ++i) {
      var result = recognition.results[i];
      var alternatives = extractAlternatives(result);
      
      alternatives.forEach(function (alternative) {
        transcripts.push(alternative.transcript);
      });
    }
    
    return transcripts.join('');
  });
  
  var results = recognitions.flatMap(function (recognition) {
    var results = [];
    
    for (var i = recognition.resultIndex; i < recognition.results.length; ++i) {
      var result = recognition.results[i];
      
      results.push(result);
    }
    
    return results;
  });
  
  var finalResults = results.filter(function (result) {
    return result.isFinal;
  });
  
  var alternatives = results.flatMap(extractAlternatives);
  
  var finalAlternatives = finalResults.flatMap(extractAlternatives);
  
  function extractAlternatives(result) {
    var alternatives = [];
    
    for (var i = 0; i < result.length; ++i) {
      var alternative = result[i];
      
      alternatives.push(alternative);
    }
    
    return alternatives;
  }
  
  function stop() {
    engine.stop();
  }
  
  return {
    stop:               stop,
    lifecycle:          lifecycle,
    recognitions:       recognitions,
    results:            results,
    finalResults:       finalResults,
    alternatives:       alternatives,
    finalAlternatives:  finalAlternatives,
    phrases:            phrases
  };
}