Sinusoidal beep in JavaScript ES5

beep.js

var audioCtx = new(window.AudioContext || window.webkitAudioContext)();
var oscillator = audioCtx.createOscillator();
var gainNode = audioCtx.createGain();
oscillator.connect(gainNode);
gainNode.connect(audioCtx.destination);

gainNode.gain.value = 1;
oscillator.frequency.value = 440;
oscillator.type = 'sine';

oscillator.start();
setTimeout(function() { oscillator.stop(); }, 500);