If a script sets 'eval' to something other than eval, the debugger becomes pretty useless, there's no way to inspect any values. This is a problem for people working in js sandboxes that disable eval, and possibly a problem for people trying to analyze malicious js. <!doctype html> <html> <head> <script> var e = 33; eval = 'thirty three'; debugger; </script> </head> </html>