How to get client information in JavaScript...???

How to gather information about your users environment including their computer platform, operating system, browser details, etc. ?

Application Code Name
var codeName = navigator.appCodeName;

Application Name
var appName = navigator.appName;

Application Version
var appVersion = navigator.appVersion;

User Language and Language
var userLanguage = navigator.userLanguage;
var language = navigator.language;

Platform
var appName = navigator.platform;

User Agent
var userAgent = navigator.userAgent;

Java Enabled
var javaEnabled = navigator.javaEnabled();

To check cookies are enabled in the browser.
navigator.cookieEnabled

CPU class of the browser's system
var cpuClass = navigator.cpuClass;

To get boolean status of system mode.
navigator.onLine;

Browser Version
var version = parseInt(navigator.appVersion,10);