Check if the page is viewed in the Safari browser in iOs

is-ios-safari.js

/* 
I want to make a bubble that explains people that they can save the page to their homescreen
I want to be absolutely sure that this is Safari on an iPhone or iPad
Not a browser in a webview in a native app
Not a browser in standalone mode
Not something else
This is the closest I can get to something I kinda trust. 
*/

var nav = window.navigator;
var ua = nav.userAgent;

function isiOsSafari (a) {
	return ("standalone" in nav) // There's a thing called standalone in nav
	 && !nav.standalone // It is not running in standalone mode
	 && ua.indexOf(a)!=-1 // iPhone is in the UA string (could be Opera)
	 && ua.indexOf('Mac OS')!=-1 // There's Mac in the UA string (not Opera)
	 && ua.indexOf('Safari')!=-1 
	 /* if all the above are true this probably means this is 
	 the Safari browser, 
	 not a webview in an app, 
	 not a page in standalone mode */
}

// Check if Mobile Safari on iPhone
if(isiOsSafari('iPhone')){
	document.write('Probably Safari on an iPhone: ' + ua);
}
// Check if Mobile Safari on iPod
else if(isiOsSafari('iPad')){
	document.write('Probably Safari on an iPad: ' + ua);
}
else{
	document.write('Probably something else: ' + ua)
}

This still detect safari on Chrome ios. Any solution?