That's one of the advantages of using programming languages where source code is distributed (e.g. Python, JavaScript, PHP), not compiled binary artifacts (C/C++, Java). You can see the source. You can even modify it and run the modified version without compilation.
It's also awesome to use Java IDEs that can show both the bytecode of .class files and also perform decompilation.
(Or back in the day, looking at the source code because we ran uncompiled stuff in Basic and whatever and that was pretty cool)