Object meta-level control on ECMA Script 5

ECMA Script 5 で新しく導入された Property descripter の話と, ECMA Script の簡単な歴史を少しだけ. Quick introduction for property descriptor, which is introduced at ECMA Script 5 and can control meta-level setting of property of object. And short history of ECMA Script (especially for ES4, 5 and harmony)