The TypeScript features in this chapter require TypeScript 1.5 or higher and the following options to be enabled in the tsconfig.json file:
"experimentalDecorators": true, "emitDecoratorMetadata": true
We are also going to need a polyfill for the reflect–metadata API. We need a polyfill because most JavaScript engines don't support this API yet. We can expect that, in the long term, this polyfill will not be required but, currently, we can use the reflect–metadata npm module: ...