Get directory from a file path or url

I am trying to get the directory location of a file, and I'm not sure how to get it. I can't seem to find a module that allows me to do this.

So for example say I have this string:

/this/is/a/path/to/a/file.html

how can I get this:

/this/is/a/path/to/a

I know I can use something like this:

path.substr(0, path.lastIndexOf("/") - 1);

But I am not sure if that is as good of a method as something that might be built in to node.

I have also tried:

var info = url.parse(full_path);
console.log(info);

and the result doesn't return what I am looking for, that gets the full path including the filename.

So, is there something built into node that can do this and do it well?