I am trying to debug a JavaScript script that gets read in a Firefox extension and executed. I only can see errors via the Firebug console (my code is invisible to Firebug), and it's reporting a "unterminated string literal."
I checked the line and the lines around it and everything seems fine-parentheses, braces, and quotes are balanced, etc. What are other possible causes that I should be looking for?
Look for a string which contains an unescaped single qoute that may be inserted by some server side code.
If you've done any cut/paste: some online syntax highlighters will mangle single and double quotes, turning them into formatted quote pairs (matched opening and closing pairs). (tho i can't find any examples right now)... So that entails hitting Command-+ a few times and staring at your quote characters
Try a different font? also, different editors and IDEs use different tokenizers and highlight rules, and JS is one of more dynamic languages to parse, so try opening the file in emacs, vim, gedit (with JS plugins)... If you get lucky, one of them will show a long purple string running through the end of file.
If nothing helps, look for some uni-code characters like
\u2028
this may break your string on more than one line and throw this error
Try a "binary search". Delete half the code and try again. If the error is still there, delete half the remaining code. If the error is not there, put what you deleted back in, and delete half of that. Repeat.
You should be able to narrow it down to a few line fairly quickly. My experience has been that at this point, you will notice some stupid malformed string.
It may be expedient to perform this on a saved version of the HTML output to the browser, if you're not sure which server-side resource the error is in.
The web page developer guessed wrong about which encoding is used by the viewer's browser. This can usually be solved by specifying an encoding in the page's header.
Scan the code that comes before the line# mentioned by error message. Whatever is unterminated has resulted in something downstream, (the blamed line#), to be flagged.