Google Codesearch will be shutdown effective January 15, 2012 but there are a number of alternatives for searching the source of publicly available codebases. Alternatives mentioned (but not explicitly endorsed) by the Codesearch team include http://koders.com, http://opensearch.krugle.org, http://grepcode.com and http://www.antepedia.com.

Of these four, Krugle seems to be the most helpful for Front End development code searches, turning up plenty of hits for "webkit", for example, whereas the others turn up mostly empty-handed.