TypeScript Language Specification Version 1.8 January, 2016 Microsoft is making this Specification available under the Open Web Foundation Final Specification Agreement Version 1.0 ("OWF 1.0") as of October 1, 2012. The OWF 1.0 is available at http://www.openwebfoundation.org/legal/the-owf-1-0-agreements/owfa-1-0. TypeScript is a trademark of Microsoft Corporation. Table of Contents 1 2 Introduction ................................................................................................................................................................................... 1 1.1 Ambient Declarations ..................................................................................................................................................... 3 1.2 Function Types .................................................................................................................................................................. 3 1.3 Object Types ...................................................................................................................................................................... 4 1.4 Structural Subtyping ....................................................................................................................................................... 6 1.5 Contextual Typing ............................................................................................................................................................ 7 1.6 Classes .................................................................................................................................................................................. 8 1.7 Enum Types ..................................................................................................................................................................... 10 1.8 Overloading on String Parameters......................................................................................................................... 12 1.9 Generic Types and Functions ................................................................................................................................... 12 1.10 Namespaces .................................................................................................................................................................... 14 1.11 Modules ............................................................................................................................................................................ 16 Basic Concepts .......................................................................................................................................................................... 17 2.1 Grammar Conventions ................................................................................................................................................ 17 2.2 Names ................................................................................................................................................................................ 17 2.2.1 Reserved Words ........................................................................................................................................................ 18 2.2.2 Property Names ........................................................................................................................................................ 18 2.2.3 3 Computed Property Names ................................................................................................................................. 19 2.3 Declarations..................................................................................................................................................................... 19 2.4 Scopes ............................................................................................................................................................................... 22 Types ............................................................................................................................................................................................. 25 3.1 The Any Type .................................................................................................................................................................. 26 3.2 Primitive Types ....................................