For instance, if I messed up something in my code and had an error, the debugger pops up. In this debugger I can not only browse the stack trace and manipulate

For instance, if I messed up something in my code and had an error, the debugger pops up. In this debugger I can not only browse the stack trace and manipulate those objects, I can actually fix what is broken and resume execution of the program from that point The developer tools in Chrome and Firefox remind me of the Smalltalk IDEs. I don't know if it's intentional or accidental, but the similarities suggest to me that some of the ideas from Smalltalk have been carried over to web development.