Answer by mgabor6 for Detect 64-bit or 32-bit Windows from User Agent or Javascript?

I've done some tests. Here are the results, hope it helps:

64 bit MacOS + 64 bit Safari or 32 bit Chrome:
window.navigator.platform=MacIntel

32 bit windows + safari:
window.navigator.platform=Win32

64 bit Windows + 64 bit IE:
window.navigator.platform=Win64
window.navigator.cpuClass=x64

64 bit Windows + 32 bit IE:
window.navigator.platform=Win32
window.navigator.cpuClass=x86

64 bit Windows + 32 Firefox (or Chrome):
window.navigator.platform=Win32

32 bit linux mint (i686) + firefox:
window.navigator.platform=Linux i686

64 bit Ubuntu (x86_64) + 32 bit Chrome:
window.navigator.platform=Linux i686

64 bit Ubuntu + 64 bit Epiphany:
window.navigator.platform=Linux x86_64

So far i've used this code:

deployJava.isWin64OS = function() {
    return navigator.userAgent.indexOf('WOW64')>-1 || window.navigator.platform=='Win64';
};