TypeScript Language Features

Abstract

TypeScript is a superset of JavaScript. That means that the TypeScript language includes the entire JavaScript language plus a collection of useful additional features. This contrasts with the various subsets of JavaScript and the various lint tools that seek to reduce the available features to create a smaller language with fewer surprises. This chapter will introduce you to the extra language features, starting with simple type annotations and progressing to more advanced features and structural elements of TypeScript. This chapter doesn't cover every feature included in the ECMAScript language specification, so if you need a refresher on JavaScript, take a look at Appendix 1.