Документы доступны только при нацеливании на Ecmascript 5 и выше.

# If you're getting the 
	"script.ts:9:8 - error TS1056: Accessors are only available when targeting ECMAScript 5 and higher."
# in typescript compliation you need to change your target for compiling in cmd
# like:
tsc -t es5 script.ts
# or
tsc -target es6 script.ts
Jenova