Firefox slow with javascript running off the hard-drive, not with uploaded files -

i'm developing javascript-based game engine. i'm running off local drive because reuploading every single small change webserver takes time.

the local copy runs fine in chrome (with --allow-file-access-from-files parameter), in firefox (v19) engine slows down massively. website loads fully, movement or clicks react until script crashes. clearing cache or closing tabs doesn't make go faster.

when upload site server however, runs fine in firefox.

i've tried disabling security.fileuri.strict_origin_policy in dev-profile. makes little faster, doesn't solve slowdowns.

is there known issue local javascript running slower in firefox?

instead of testing code on file: url, why not use local web server? should run same on other web server, , able test app in browsers without fiddling security settings.

what os running? can install xampp on of popular oses. on windows, people prefer uniform server. on osx can use xampp or built-in web server.

then save files in local web server's htdocs directory on other server, , load app either localhost: url, or better yet, use own machine's hostname whatevermyhostnameis: url, avoid special security treatment localhost may receive.