When the script is loaded twice, it causes an infinite loop

[alexlehm]

The script is not properly guarded against loading it more than once, if it is, the error reporting goes into an infinite loop and reports the first error over and over essentially halting the browser.

The variable fnPreviousOnErrorHandler is overwritten with the error handler of jsErrLog so that the method to call the previous handler will the own handler.

It would be best to put the whole script into the if (!jsErrLog) backets. This way only one "instance" is created and the variables are not overwritten when the script is accidentally loaded twice.