Browser Bugs & Inconsistencies

I ran into a hard-to-find bug today. After a while I figured out that IE cleared one of my hashes, for seemingly no good reason. This was my code:

for (var p in hash) {
    hash["x_" + p] = hash[p];
    delete hash[p];
}

I actually didn’t manage to reproduce this behavior outside of my original script, instead IE would go into an infinite loop and rapidly claim all available memory when the code ran.