In that case it doesn't need a final semi-colon because the last part of the script is a "for" loop. A for loop normally looks like this when you have it spaced out more naturally:

for ( var i = 0; i < 10; ++i )
{
do_something();
do_something_else();
}

It doesn't normally need an extra semi-colon after the final closing } brace of the for loop. But it won't do any harm if you put one in, it is just the equivalent of an empty statement after the for loop.

Some other constructs do expect semi-colons, like at the end of function calls or variable assignments (like you can see _inside_ the for loop above). Actually some of those are also optional in the JavaScript language in certain circumstances, but it is best to put those ones in.

- Michael