TypeScript

with Tom von Clef

KnoxvilleJS

April 21, 2014

About Me

Programming Since Age 11

At the Electric Power Research Institute

Software Developer with 5 years experience

Finished BS in Comp Sci from UT in 2012

Mostly full-stack web development

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My Project

Ridiculous Project Deadline

• No postback client-side with AJAX queries
• ~400 lines of JS
• Previous iteration was hurried
• Needed to quickly add much more
• Getting hard to work with
• So I turned to...

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TypeScript!

JavaScript enhanced for large applications

• Strict superset of JavaScript
• Optional static types, OOP, and modules
• Produces clean, idiomatic JavaScript

TypeScript Background

• Microsoft led project, first announced in Oct 2012
• At version 1.0 (April 2 release)
• Included in Visual Studio 2013 (extension for VS2012). Also node.js. And Sublime Text, Vi, Emacs, syntax files
• Open Source (Apache License 2.0)
• Created by Anders Hejlsberg

Anders Hejlsburg

• Original author of Turbo Pascal
• Chief architect of Delphi
• Lead architect of C#
• Now… TypeScript

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The TypeScript Playground

TypeScript compiler written in TypeScript

http://www.typescriptlang.org/Playground/#src=

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TypeScript features...

Type Annotations

Compile Time Checking

Classes

Inheritance

Interfaces

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Modules

Enums

Generics

Function Expressions

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...make JavaScript feel like C#

TypeScript Advantages

• Low Risk: Idiomatic & pretty JavaScript output
• Easy to debug
• Makes it simple to migrate to/from TypeScript
• Better structuring: modules, classes, interfaces
• No inadvertent globals, other “Bad Parts”
• ES6 now (classes, modules…)
• Optional types offer
• Compile time checks
• Auto-complete
• Automatic type inference

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TypeScript Disadvantages

• Hard to name many disadvantages, since it is a superset of JavaScript
• But it does require that extra compile step and source-mapping
• Lack of type union

DefinitelyTyped

• Types for 375+ JS libraries
• From 401 contributors
• https://github.com/borisyankov/DefinitelyTyped
• Submitted something for jquery.flot.js
• It’s cool getting your own code back through NuGet

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My Plan for Future Use of TypeScript

• Going forward
• Won’t use TypeScript for < 200 lines JavaScript
• …but they can easily be converted to TS if they get larger.
• Plan to use it for larger web applications

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Where to Go Next

www.typescriptlang.org

CodePlex

www.infoq.com/presentations/typescript-tooling

TypeScript Spec is very readable:

www.typescriptlang.org/Content/TypeScript Language Specification.pdf

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Questions?