Solution 1:

Using a mix of feature detection and Useragent string:

    var is_opera = !!window.opera || navigator.userAgent.indexOf(' OPR/') >= 0;
    var is_Edge = navigator.userAgent.indexOf("Edge") > -1;
    var is_chrome = !!window.chrome && !is_opera && !is_Edge;
    var is_explorer= typeof document !== 'undefined' && !!document.documentMode && !is_Edge;
    var is_firefox = typeof window.InstallTrigger !== 'undefined';
    var is_safari = /^((?!chrome|android).)*safari/i.test(navigator.userAgent);

Usage:
if (is_safari) alert('Safari');

Or for Safari only, use this :

if ( /^((?!chrome|android).)*safari/i.test(navigator.userAgent)) {alert('Its Safari');}

Solution 2:

The following identifies Safari 3.0+ and distinguishes it from Chrome:

isSafari = !!navigator.userAgent.match(/Version\/[\d\.]+.*Safari/)