When I first load a page in the Firefox debugger, no source files are shown, so it is not possible to set breakpoints until an error occurs (I don't want to have to insert "debugger;"). Is there a fast way to start running, stopping at the first executable JavaScript line? I tried Stepping In, which I thought should do this, but it does not do anything, probably because it only works when paused at a breakpoint.
I searched the Web and could not find any solution, even though this seems to me a common problem. Am I missing something obvious?