support of `iterator.return()` – Of course, @@iterator is supported • You can easily create the custom iterators • destructuring – Array, Object patterns are already supported – Rest element is just supported (WK) – Destructuring accepts iterators (WK) – Spec conformance becomes higher than Firefox 40
String#repeat etc. • Array extra methods – Array#find etc • Object extra methods – Object.assign, Object.getPrototypeOf etc. • Math extra methods – Math.imul etc. • Number extra methods
write builtin functions in JS – For example, Array#sort is rewritten in JS – Bucket & merge sort • Privileged JS code can emit bytecodes – @putDirectByVal • JS-written builtin encourages DFG/FTL JIT – ArrayIterator#next is written in JS • Inlining • Object sinking