Typescript Mini Reference: A Quick Guide to the Typescript Programming Language for Busy Coders

Preface....11 Dear Readers:....14 1. Introduction....16 2. Typescript Basics....22 2.1. What is Typescript?....22 2.2. Static Typing....26 2.2.1. Type annotations....26 2.2.2. Static type checking....26 2.2.3. Type inference....28 2.3. Notes on Development Process....29 2.4. The Typescript Compiler....31 2.5. Typescript JSON Configuration File....34 2.5.1. Top-level options....34 2.5.2. compilerOptions....36 2.5.3. strict....39 2.5.4. strictNullChecks....39 2.5.5. noImplicitAny....40 2.5.6. noImplicitThis....40 3. Module System....42 3.1. ES Modules....42 3.2. Typescript Modules....43 3.3. Module Exports....43 3.3.1. (Regular) exports....44 3.3.2. Default exports....46 3.4. Module Imports....47 3.4.1. Module import....47 3.4.2. import - from Declaration....48 3.4.3. Default import....48 3.4.4. Name list import....48 3.4.5. Namespace import....49 3.5. Typescript Namespaces....49 4. Variables....50 4.1. The const Declaration....50 4.2. The let Declaration....51 4.3. The var Declaration....53 5. Basic Types....55 5.1. Javascript Types....55 5.1.1. The typeof operator....56 5.1.2. The instanceof operator....57 5.2. Strict Equality....58 5.3. Primitive Types....59 5.3.1. The boolean, number, and string types....59 5.3.2. The bigint Type....60 5.3.3. The symbol type....60 5.4. Literal Types....61 5.5. The any Type....62 5.6. The unknown Type....63 5.7. The null and undefined Types....65 5.8. The never Type....67 5.9. The void Type....68 5.10. The object Type....69 5.11. Function Types....70 5.12. Array Types....71 5.13. Tuple Types....72 5.14. Enum Types....74 6. Type Aliases....76 7. Type Annotations....79 7.1. Variable Annotations....79 7.2. Function Annotations....80 8. Assertions....84 8.1. Type Assertions....84 8.2. Const Assertions....85 8.3. Non-Null Assertions....87 9. Generics....89 9.1. Why Generics?....89 9.2. Generic Functions....93 9.3. Generic Types....95 9.4. Generic Type Constraints....96 10. Arrays....98 10.1. Generic Array....98 10.1.1. Array creation....99 10.1.2. Array iteration....100 10.2. Generic ReadonlyArray....101 11. Algebraic Data Types....103 11.1. Tuples....103 11.1.1. Fixed-size tuples....103 11.1.2. Generic tuples....105 11.1.3. Variadic tuples....105 11.2. Readonly Tuples....108 11.3. Union Types....109 11.3.1. Narrowing....111 11.4. Discriminated Unions....112 11.5. Intersection Types....114 12. Function Types....116 12.1. Function Definitions....116 12.2. Arrow Function Definitions....117 12.3. Function Types....118 12.3.1. Function type expressions....118 12.3.2. Function return types....120 12.3.3. Generic function alias....121 12.3.4. The Function type....121 12.4. Parameter List....122 12.4.1. Parameter initializers....123 12.5. Optional Parameters....123 12.6. The Rest Parameter....125 12.7. Parameter Destructuring....128 12.8. The this Parameter....130 12.8.1. Global context....131 12.8.2. Function context....131 12.9. Typescript Function Overloading....133 12.9.1. Overload signatures vs the implementation signature....133 13. Object Types....136 13.1. Object Literal Types....136 13.1.1. The empty object literal type....138 13.2. Object Type Members....139 13.2.1. Optional properties....139 13.2.2. Readonly properties....140 13.3. Index Signatures....142 13.3.1. Typescript index signatures....143 13.4. Getters and Setters....145 13.5. Member Methods....148 13.5.1. Method overloading....149 13.6. Structural Subtyping....149 14. Interfaces....152 14.1. Interface Types....152 14.2. Extending Interfaces....154 15. Classes....156 15.1. The ECMAScript Class....156 15.1.1. Class declaration....156 15.1.2. Class body....157 15.1.3. Fields....158 15.1.4. Accessors....159 15.1.5. Methods....159 15.1.6. Constructors....159 15.1.7. Static blocks....160 15.1.8. Inheritance....160 15.2. The Typescript Class....160 15.2.1. Constructors....161 15.2.2. Member visibility....162 15.2.3. Parameter properties....163 15.3. Abstract Classes....164 15.4. Implementing Interfaces....166 15.4.1. Implementing multiple interfaces....168 15.5. Generic Classes....169 16. Type Narrowing....171 16.1. Control Flow Analysis....171 16.2. The typeof Type Guard....171 16.3. The instanceof Type Guard....172 16.4. The in Operator Narrowing....174 16.5. Discriminated Unions....175 17. Advanced Types....179 17.1. Template Literal Types....179 17.2. The typeof Type Operator....180 17.3. The keyof Type Operator....181 17.4. Indexed Access Types....182 17.5. Conditional Types....183 17.6. Mapped Types....184 Appendix A: How to Use This Book....186 About the Author....190 About the Series....192 Community Support....194