speech.js

// See: https://bugs.chromium.org/p/chromium/issues/detail?id=799849
var grammar = '#JSGF V1.0; grammar commands; public <command> = left | right | jump | duck ;'
var recognition = new webkitSpeechRecognition();
var speechRecognitionList = new webkitSpeechGrammarList();
speechRecognitionList.addFromString(grammar, 1);
recognition.grammars = speechRecognitionList;
recognition.continuous = true;
recognition.lang = 'en-US';
recognition.interimResults = false;
recognition.maxAlternatives = 1;

recognition.onresult = function(e) {
	var command = e.results[e.results.length - 1][0].transcript;
	console.log(command);
};

recognition.start();