Hello @kartik,
Try this:
var OSName = "Unknown";
if (window.navigator.userAgent.indexOf("Windows NT 10.0")!= -1) OSName="Windows 10";
if (window.navigator.userAgent.indexOf("Windows NT 6.2") != -1) OSName="Windows 8";
if (window.navigator.userAgent.indexOf("Windows NT 6.1") != -1) OSName="Windows 7";
if (window.navigator.userAgent.indexOf("Windows NT 6.0") != -1) OSName="Windows Vista";
if (window.navigator.userAgent.indexOf("Windows NT 5.1") != -1) OSName="Windows XP";
if (window.navigator.userAgent.indexOf("Windows NT 5.0") != -1) OSName="Windows 2000";
if (window.navigator.userAgent.indexOf("Mac") != -1) OSName="Mac/iOS";
if (window.navigator.userAgent.indexOf("X11") != -1) OSName="UNIX";
if (window.navigator.userAgent.indexOf("Linux") != -1) OSName="Linux";
Hope it helps!!
Thank you!!