Cómo obtener la versión de JavaScript y JScript

//--------------------------------------------------------------------------------------------------
// Engines      JavaScript   1+
//              JScript      1+
// Environments NN2+ IE3+ WSH1+ MOZILLA1+ SAFARI1+
//--------------------------------------------------------------------------------------------------

// Global
//--------------------------------------------------------------------------------------------------

function  __this() { return this; }
var __g = __this();

//--------------------------------------------------------------------------------------------------

var __err_t = __g.Error;
var __num_t = __g.Number;
var __rex_t = __g.RegExp;

// JScript
//--------------------------------------------------------------------------------------------------

var  __jsm_; /*@cc_on __jsm_ = @_jscript_version; @cc_off @*/       
if (!__jsm_)
     __jsm_ = __err_t ? 5 : (__rex_t ? 3 : (__num_t.MAX_VALUE ? 2 : 1));

// JavaScript
//--------------------------------------------------------------------------------------------------

var __jsn_ = __err_t ? 1.5 : (__g.Infinity ? 1.3 : (__rex_t ? 1.2 : (__num_t.MAX_VALUE ? 1.1 : 1))); 

if (__jsn_ == 1.5)
    __jsn_ = eval('[]').reduce ? 1.8 : (__g.Iterator ? 1.7 : (eval('[]').map ? 1.6 : 1.5));