errors. Provide a structuring mechanism for larger pieces of code. Impose no runtime overhead on emitted programs. Emit clean, idiomatic, recognizable JavaScript code. Produce a language that is composable and easy to reason about. Align with current and future ECMAScript proposals. Preserve runtime behavior of all JavaScript code. Avoid adding expression-level syntax. Use a consistent, fully erasable, structural type system. Be a cross-platform development tool. Do not cause substantial breaking changes from TypeScript 1.0. https://github.com/microsoft/TypeScript-wiki/blob/master/TypeScript-Design-Goals.md#goals