REAPER script: Unbypass and online all FX for selected tracks

Enable FX on track select.lua

-- Unbypasses and onlines all FX for selected tracks
--
-- Released to the public domain.

lastSelection = ''

function enableFX()
    -- Track: Unlock track controls
    reaper.Main_OnCommandEx(41313, 0, 0)    
    -- Unbypass FX of selected tracks
    cmd = reaper.NamedCommandLookup('_XENAKIOS_UNBYPASSFXOFSELTRAX')
    reaper.Main_OnCommandEx(cmd, 0, 0)
    -- Set all FX online for selected tracks
    reaper.Main_OnCommandEx(40536, 0, 0)
end

function main()
    selection = ''
    idx = 0
    while true do
        track = reaper.GetSelectedTrack(0, idx)
        if track then
            selection = selection .. reaper.GetTrackGUID(track)
            idx = idx + 1
        else
            break
        end
    end

    if lastSelection ~= selection then
        lastSelection = selection
        enableFX()
    end
    reaper.defer(main)
end

main()