TypeScript - Javascript done right
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This is an introductory presentation of the TypeScript language. It cover its genesis, its features and its use in Visual Studio 2012
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TypeScript - Javascript done right
- 1. TypeScript Javascript Done Right Wekoslav Stefanovski Seavus 24.10.2012
- 2. Agenda • A little bit of history • Why is TypeScript needed – design goals • Using TypeScript (with Visual Studio or without) • TypeScript declaration – Types and type annotations – Classes – Interfaces and structural types – Modules • Why should I use TypeScript today? • Q&A
- 3. Who am I Wekoslav Stefanovski Senior Developer Seavus - Javascript (ab)user since 2000 - C# user since 2001 - Joined the Ajax and XHR fun in 2006 - Member of the Macedonian .NET user group - Co-leader of the Macedonian Visual C# user group
- 4. A little bit of history • What is this thing called Javascript??? • Prototype-based dynamic scripting language • Build in Netscape in 1995, initially focused on non-professional developers. • Created by Brendan Eich in a 10-day hack session. • Standardized as ECMAScript (in 1999), still plenty incompatible “dialects” • We were somewhat lucky, it could have been VBScript
- 5. Why is TypeScript needed? • Javascript’s got 99 problems but types ain’t one – Variable hoisting – Some very idiosyncratic behaviors – No explicit includes – The this parameter can be actually that – Abysmal debugging experience – Browser DOM incompatibility is not due to Javascript • ECMAScript 6 standard specification is a long way off • Implementations are even further away
- 6. Why is TypeScript needed? • Still people have to use it • It’s lingua franca of the web • People have build many great product using it: – jQuery – Ext JS – GWT – Knockout – Backbone.js – JSLint / JSHint – Node.js
- 7. What exactly is TypeScript? • TypeScript is a language for application-scale Javascript development • TypeScript is a typed superset of JavaScript that compiles to plain Javascript • Any browser. Any host. Any OS. • Open Source • What TypeScript does is, it basically formalizes a static type system that describes JavaScript's dynamic types, but it describes them at development time. (Anders Hejlsberg)
- 8. TypeScript design goals • Extend Javascript to facilitate writing large applications. • Superset of Javascript • Development tooling support • Compiled Javascript that runs on any Javascript execution environment (Chakra, V8, Node.js…) • Start with Javascript and add things here and there • Generate pretty, idiomatic Javascript
- 9. Using TypeScript • Source file / declaration file code organization – .ts for source files – .d.ts for declaration files. – (analogous to .h and .cpp in C++) • Type safety, intellisense and compile errors • Declarations can be created for existing Javascript libraries – DOM and jQuery declarations provided with TypeScript – Possible to write your own for any existing Javascript library
- 10. Using TypeScript with Visual Studio • Tooling support – Static type checking. – Strong type inference. – Symbol-based navigation. – Statement completion / intellisense. – Code refactoring. • Plug-in available for download
- 11. Using TypeScript without Visual Studio • Support available for most popular code editors (Eclipse, Sublime Text, EMACS, Vim…) • Node.js package available (typescript) • Command line compiler (tsc).
- 12. TypeScript declaration • Any (currently most) valid Javascript is valid TypeScript • Closely aligned with existing ECMAScript 6 proposals
- 13. TypeScript types and type annotations • Optional static typing • Applied using a post-fix syntax • Support for built-in Javascript types (number, string, boolean, null, undefined, void) • Return type of the function can be inferred. • Supports optional types via ? Operator • Subtypes of the Any type • Supports typed arrays
- 14. TypeScript arrow notation • New feature planned for ECMAScript 6. • Compact form of function expressions that omit the function keyword. • Similar to lambda expressions in C#. • Lexical scoping of this. var messenger = { message: "Hello World", start: function() { setTimeout(() => { alert(this.message); }, 3000); } }; messenger.start();
- 15. TypeScript interfaces and structural types • Designed for development tooling support only. • Interfaces have no run-time representation - they are purely a compile-time construct. • Structural type system - interfaces are automatically implemented by any object/prototype that complies structurally. • Supports overload by parameter signature. • Supports implementing multiple interfaces.
- 16. TypeScript classes • Classes are alike to the proposed classes for ECMAScript 6. • public or private member accessibility. • Parameter property declarations via constructor. • Supports single-parent inheritance. • Derived classes make use of super calls to parent. • Do not support overloads yet.
- 17. TypeScript modules • Analogous to .NET namespaces. • Prevents global variable naming collisions. • Closely aligned with those proposed for ECMAScript 6. • Allows hiding implementation detail • Allows exposing a public API.
- 18. Why should I use TypeScript • Open Source, hosted on codeplex!!! • Tooling support, for type safety, inference and refactoring!!! • Static types and compilation helps catch mistakes & bugs earlier!!! • Structural interfaces & typing!!! • Compiles to idiomatic JavaScript!!!
- 19. Why should I use TypeScript (today) • Support for ECMAScript 6 today!!! • Works alongside existing code!!! • Does not hold your .js files hostage!!! • Anders Hejlsberg is involved!!!
- 20. Why shouldn’t I use TypeScript • It is a remove (albeit a slight one) from the Javascript sources. • Only at version 0.8 (and it shows) • Limited availability of resources & libraries (can use any existing JavaScript, albeit with limited type safety and tooling support). • No support for generics (yet, but is defined in spec). • All types are nullable. • Limited tooling support outside of Visual Studio 2012 or Monaco web editor.
- 21. ?
- 22. Thank you for your attention.
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