Send mail after found new items inside the folder
Change your code so that the do script captures a return value and use that to decide what to do. For example:

tell application "Safari"
    activate
    set theScript to "new Date().toJSON().slice(0,4);"
    set theResult to do JavaScript theScript in current tab of first window

    if theResult is "2014" then
        display dialog "IT IS 2014"
    end if
end tell