I have a Javascript application that relies on capturing keyboard events in a textarea. While testing and debugging it on Firefox (14.x) with firebug (1.10.2) I noticed that my application behaves differently when I have breakpoints active and the debugger is working.
I know how to detect Firebug but I would like to know if it is possible to detect (with Javascript) when the Firebug is actually used for debugging?
Edit: here is an example on some random site
This site catches the key event in an input box, prints out character code and replaces the pressed key with a text representation (ie. "enter" for enter key) or an uppercase (if a letter).
When I debug it with Chrome and place a breakpoint on the listener function, nothing happens when the breakpoint is reached (as expected), when I resume the script the text is printed out as normal.
When I debug it with Firebug on Firefox: Let us say that previously I pressed the "e" letter and the input bar contains text "E". I turn on the breakpoint and press letter "z". Firebug stops at the breakpoint but the input bar now has text "Ez" instead of "E". When I resume the script, this text is replaced with "Z" as expected.
I tried out another Firefox debugger (Venkman 0.9.89) and the same thing happened. So my guess is this is a Firefox problem, not the debugger problem. So the question might be more general, can it be detected when is the Javascript code being debugged?