js判断安卓 or ios

<script>
	document.querySelector('.download').addEventListener('click', function() {
	    var ua = window.navigator.userAgent;
	    if (ua.match(/Android[\s\/]([\d\.]+)/)) {
	      alert('这是安卓机')
	    } else if (ua.match(/(iPhone|iPad|iPod)/)) {
	      alert('这是iphone')
	    }
	  });
</script>