Debugging Web Workers
While working on FileReader.js Web Worker file processing with FileReaderSync, I needed to figure out what was going on with the script inside a web worker. It can be very difficult to track down errors without standard developer tool support, like logging and debugging. Luckily, in Chrome Devtools, this is possible.
How to do it
It can be a little tricky to find, but click over to the ‘Scripts’ panel, and expand the ‘Workers’ accordion on the right. Then check the ‘Pause on Start’ checkbox and you will enter the debugging mode once the worker gets fired up. Here is a screenshot of the relevant checkbox:
Here is a screencast of me playing with this feature: