How to get Chrome debugger to break or error when working on undefined variables
My Javascript code (hundreds of lines) hangs Chrome and when I debug the issue I find out that a variable was undefined. I don't get errors in the console. So this is making my debugging more time consuming because there are no errors or exceptions or anything that tells me where the issue is.
I don't want to add debugging code. Is there a way to make the debugger put out an error, break in the debugger or give an exception or show anything useful for the developer when hitting an undefined variable during runtime? It doesn't have to be for Chrome only.
Answer
You can break into the DevTools debugger when a JavaScript error occurs using the Pause on JavaScript Exceptions feature. It has two active modes; pause on all exceptions, and pause on uncaught exceptions.
Based on the description of your experience, the application you are working on may have errors that are caught but not re-thrown or logged. Using the "Pause on All Exceptions" (blue colored pause icon), will help in this scenario.
Note: some libraries, like jQuery, catch exceptions and do not re-throw them. If you have this experience, you may need to advance past these exceptions or set the "Pause on All Exceptions" feature after all dependencies have loaded.