WebKit Apocrypha

The central data structure in JavaScriptCore is JSValue. It represents the value of a JavaScript variable. Since there are no type restrictions in JavaScript, a JSValue can contain anything from a simple bool constant to an object. Most operations work on these JSValues, so their effective handling is essential for a fast JavaScript engine. In JavaScriptCore there are 3 types of JSValue representations: JSValue32 and JSValue32_64 for 32 bit machines, and JSValue64 for 64 bit machines. Albeit maintaining all of these representations is a heavy burden, the feeling to have a fast JS engine is rewarding.