Speech Synthesis JS API

speaker.js

speech = function (msg, options, onend) {
        this.text = msg;
		this._defaults = {
			voiceURI: 'native',
			volume: 3,
			rate: 2,
			pitch: 1.5,
			lang: 'en-US'
		};
    this.defaults = options !== undefined ? options : this._defaults;
		this._createSpeech = function () {
            console.log(this.defaults);
			var defaults = this.defaults,
				speech = new SpeechSynthesisUtterance();
			speech.voiceURI = defaults.voiceURI;
			speech.volume = defaults.volume;
			speech.rate = defaults.rate;
			speech.pitch = defaults.pitch;
			speech.lang = defaults.lang;
			return speech;			
		}, 
		this._onend = function (e) {
			console.log('finished in '+ e.elapsedTime)
		};
        var speech = this._createSpeech();
        speech.text = this.text;
        speech.onend = onend !== undefined ? onend : this._onend;
        return speechSynthesis.speak(speech);
}
 
var derp = new speech('Hi, My name is Tahza. How can I help you today.');
var notFound = new speech('Trouble loading your worms. Please try again later', {volume: 9,rate: .2, pitch: .4});

Second version is an actual returnable object, where you can modify the options if necessary.