How did they do that? a fast (database) filter, like Spotlight

There’s a site where there appears to be a long list of people and their titles and locations, and when you type in the filter, like the name “John” for example, it will show all "John"s in ***real ***time, kind of like Spotlight on Mac OS X. The site is here:

http://www.weil.com/people/

Does anyone know how this is done? Or perhaps more relevant to me, does anyone know if there is some easy way for me to accomplish this myself – like with a Javascript library or something?
Thanks.