在Android上调试javascript时如何查看断点（并查看错误行号）？

Question

I'm trying to follow these instructions for debugging android javascript.

I am aware of How can I debug javascript on Android? , but it's not clear to me how (or if) I can hit breakpoints - either using Chrome on the Android device, or the Android browser.

I can see and 'inspect' the device OK:

But breakpoints don't get hit, nor can I see line numbers on the errors in the console:

Between these two problems, I'm not getting much useful information from the debugging experience! I have tried going to 'about:debug' in the android browser, and do see the debug options appear.

I will add that the js I am debugging works fine in the latest Chrome on the same Android device.

Answer 1

First off, it seems like there are a bunch of syntax errors that may be preventing mustache.js from executing at all - see if you can take care of those first.

I'd try setting a breakpoint on the next line down - line #9 - to see if anything in that IIFE is running at all.

Answer 2

Assuming you are using a module bundler (such as Webpack) in development (based on port 8080 in your screenshot), most likely the code you're trying to debug is executed via eval . In which case by the time you can see it in the devtools, it has already run.

You can either use the debugger statement in your code, or running in production mode - where there's a real script file being executed. In both cases, you should attach the remote debugger first, and only then navigate to your page (or refresh it).

Answer 3

I have now tried the same thing again, and this time didn't experience the problem. Unfortunately I can't put my finger on what the problem was exactly, as due to my dev machine dying I am running a new windows 10 installation, and potentially a different version of the Android SDK and ADB. The phone and android browser haven't changed.

Anyway, I can now set and hit breakpoints as I'd expect:

I also get better error descriptions and line numbers:

FWIW, the only problem that needed fixing was changing some 'let' declarations to 'var'.