There are two way to check.first is you can directly check whether key contain A or not in binding like this:-. but i think this is not the better way so instead of this you can use ko.computed to check.
Check for operating system information in Windows 7. 1  Click the Start button , enter Computer in the search box, right-click Computer, and then click Properties. 2  Look under Windows edition for the version and edition of Windows that your PC is running.
Check for operating system information in Windows 10. 1  Go to Start , enter About your PC, and then select About your PC. 2  Look under PC for Edition to find out which version and edition of Windows that your PC is running.  Look under PC for System type to see if you're running a 32-bit or 64-bit version of Windows.