Interesting method to do multi-value-testing in JS

javascript-multitester.js

({abc:1,def:1,jkl:1}[xyz])
// nearly the same as:
( xyz=="abc" || xyz=="def" || xyz=="jkl" )

// and....

(function(){switch(pn) {
	case "prv":return "previous";
	case "nxt":return "next";
}})()
// returns the same as:
(pn=="prv"?"previous":(pn=="nxt"?"next":undefined))
// which returns the same as:
({"prv":"previous","nxt":"next"}[pn])