i just wanted to raise awareness that javascript needs some caution when it comes to accessing object propreties.

if userdata is used as a key you might indeed make your dictionary partly unusable for your code. imagine: d[name]='foo' and the name is provided from the user... better make sure the user cannot select "toString" as the username if you want to use that function in your code. "hasOwnProperty" allows some shielding around the issue.