Development Blog

The first Firebug feature I worked on was a whopper: eval() debugging.  One of the challenges is how to name the source code buffer.

By default Firefox names the eval() buffer using the containing filename. This is a disaster:  it’s the debugger equivalent of overstrike: eval functions overlap orginal functions.

Coming up with an alternative is not so easy. The name has to uniquely identify the buffer to support breakpoints and yet be understandable by developers. The Firebug default is to compute an MD5 hash for the buffer then show the developer a string related to the calling file and the source.

Firebug also supports developer-named eval() buffers: just add a line to the end of your eval(expression) like:

//@ sourceURL=foo.js

This makes the source appear to come from the calling domain at file foo.js. The syntax of the line needs to match this regular expression:

const reURIinComment = /\/\/@\ssourceURL=\s*(\S*?)\s*$/m;

sroussey points out that this feature has recently been added to Webkit so it should also work in Safari.

jjb

Followup in the newsgroup please.

This entry was posted on Tuesday, August 11th, 2009 at 10:44 pm and is filed under Firebug Docs, Firebug Feature. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.