This page will collect various techniques for achieving common tasks needed in writing user scripts. Discussion about limitations, relative portability, and speed of the various alternatives is strongly encouraged. There is a lot of duplication and non-optimal efforts out there, and this will hopefully encourage us to write tighter, more correct code, both easier and faster.
An advanced API for interacting with Wikipedia content is being developed, large parts of which are already operational. The various possibilities are described at mw:API. The idea is to send an AJAX request (see below) to the API containing a query. The result of this query can be returned in several formats, of which JSON is perhaps the most useful, see below.