Debgging Javascript 'undefined' message box

Question

I have a web-app I have been using and working on for a while now. Today it randomly started to popup a message box with the word 'undefined' consistently when I press a submit button

-There are no alert messages with a variable in the javascript.
-The only changes I have made since the error are to gitignore
-The webabb still runs completely fine except for this message

I am using eclipse IDE and trying to debug this through a local tomcat server. Is there anyway to gain a closer look at what is happening in Javascript at runtime?

Is there anything that would cause a popup message of this type in javascript?

Answer 1

No matter what IDE you are using, you can always debug JavaScript code from within the web browser. If you do not yet have the Chrome web browser, you should download it. It is an excellent web development tool. Once you have it installed, navigate to the following page and follow the tutorial on debugging JavaScript code with breakpoints:

https://developers.google.com/chrome-developer-tools/docs/javascript-debugging#breakpoints