Migrating to TypeScript

TypeScript is a superset of ES6 and, as its name suggests, uses a type system.This can have an enormous impact on developer tools, providing richerauto-complete and static analysis.

Angular was built using TypeScript, and supports decorators which provide metainformation to Angular. While it is possible to use Angular without these features, the syntax feels more "natural" with TypeScript's decorators.

原文: https://angular-2-training-book.rangle.io/handout/migrate/migration-prep/migrate_to_typescript.html