How to explore NSBundle contents?

Question

I've got NSBundle file named main.jsbundle packaged by react-native bundle, which tool I can use to explore it's contents? I can see that it got the minified js code inside, and also some sort of index at the beginning of file. I need to extract the js code in order to debug an issue.

Answer 1

As @ivanmoskalev pointed out, this might not be necceserily NSBundle. Anyway, piping the file through strings outputs pretty much just the javascript part of the file, so that works for me.

Answer 2

NSBundle is a totally different thing – it is a native class representing an Apple format of packaging applications and frameworks, allowing to access and manipulate it from native code.

You are asking about a React Native bundle, which is quite a loose concept of a single file of minified JS code + an assets folder for images and data. You can actually de-minify the js-bundle using conventional tools such as uglify-js and try to inspect it.

You can also use sourcemaps produced by Metro, and maybe metro-symbolicate to understand how the minified code from the bundle maps to actual sources, although I can't recommend anything more specific without knowing the problem at hand. There is also no documentation for metro-symbolicate, meaning you'll have to grok its sources.