A couple of Sizzle micro-optimisations
First - there's a lot of testing whether
- typeof selector !== "string"
(or whatever) - might be useful to define the strings "string", "undefined" etc. as a variable STRING, UNDEFINED - wouldn't make any difference to the code, but minifiers would find it useful, since they could create there own minified var. Would save a few bytes.
Second - there's quite a lot of comparison to null and not-null - but usually == instead of ===. Either it's meant to be coerced (in which case just do !(whatever)) but I reckon would be better to do a proper comparison to undefined or false or empty or zero or whatever.
A