Post on 17-May-2015
description
TypeScript = JavaScript (almost) done rightMaurice de Beijer
Who am I
Maurice de Beijer
The Problem Solver
Microsoft MVP since 2005
DevelopMentor instructor
Twitter: @mauricedb
Blog: http://msmvps.com/blogs/theproblemsolver/
Web: http://www.HTML5Support.nl
E-mail: Maurice.de.Beijer@gmail.com
Agenda
What is TypeScript?
Why do we need TypeScript?
What is wrong with JavaScript?
TypeScript features
Type annotations
Type inference
Modules
Classes
What is TypeScript?
An open source programming language developed at Microsoft
By Anders Hejlsberg, lead architect of C#
A super set of JavaScript
All JavaScript is valid TypeScript
Adds optional type checking, classes, interfaces and more
Compiles to “normal” JavaScript
Either ECMAScript 5 or ECMAScipt 3
Why do we need TypeScript?
JavaScript was designed for small scripts
These days JavaScript applications get bigger and more complex
Gmail is reported to have 443,000 lines of JavaScript in 2010
This trend will continue
Single Page Applications in the browser
Node.js on the server
What is wrong with JavaScript?
Douglas Crockford on TypeScript
Microsoft's TypeScript may be the best of the many JavaScript front ends. It seems to generate the most attractive code. And I think it should take
pressure off of the ECMAScript Standard for new features like type declarations and classes. Anders has shown that these can be provided nicely by a preprocessor, so there is no need to change the underlying
language.
I think that JavaScript's loose typing is one of its best features and that type checking is way overrated. TypeScript adds sweetness, but at a price.
It is not a price I am willing to pay.
Things TypeScript adds to JavaScript
Type annotations
Type inference
Modules
Classes
Interfaces
Based on the ECMAScript 6 proposed standard
Type annotations
Type inference
Type annotations/arrays
Type annotations/param arrays
Arrow functions
Type annotations/casts
TypeScript type definitions
The DOM and standard JavaScript types are provided
Modules
Interfaces
Interfaces
Interfaces & function overloading
Interfaces & type definitions
Classes
Classes & constructors
Classes & constructors
Classes & properties
Arrow functions revisited
Arrow functions revisited
Classes & inheritance
TypeScript is still JavaScript
Not all JavaScript problems are solved by TypeScript
Some older browsers support ECMAScript 3 (December 1999)
Some older browsers have non standard DOM/CSS implementations
jQuery remains an extremely useful library
Conclusion
TypeScript is not perfect
But it helps a lot
You are not forced to use a new language
Leverage existing JavaScript skills en libraries
Consider it for your next “large“ JavaScript project
After all the risk is small