Syntax errors in JS code do not get reported to end-user

[jeremysinger]

Sometimes, syntax errors in the code window are silently suppressed when the user clicks 'Run code' - so the user doesn't know that an error has occurred. Instead there is no output. We need to report syntax errors (and maybe helpful hints) to the user.

This may be complicated by the user of the acorn parser to preprocess the code before we eval it.

[jeremysinger]

some error messages are reported ... others fail silently.

The worst one is when a variable is used without being defined - these fail silently and this is a common problem.

We need more obvious error reporting for the learners