typedef

Typedef

Typedef is a lightweight library (1.7 KB, 4.7 KB with underscore.js bundled in) that brings some much-needed sanity to object-oriented programming in Javascript. These features will feel very familiar and refreshing to anyone experienced in a more civilized staticly-typed language like C# or Java.

Typedef introduces two interesting concepts for Javascript: class member decorations, and the idea of "define-time" (semi-static) checking. In addition it rolls in classical-style inheritance, interfaces, and mixins.

The goal is to let you build scalable web apps with a rich class hierarchy using proven object-oriented concepts and semantics-enforcing constructs. Wed with the dynamic nature of Javascript-- it's a potent mix.

The Javascript romantic in you may recoil and shout back about the virtues of embracing the native prototype-style inheritance model. This is understandable-- but if you can unburden yourself from the limitations you've built around the language and keep an open mind... you're in for a wild ride.

Feature Overview

• Class inheritance. Classical inheritance goodness in Javascipt. Create a rich class hierarchy that feels sane, with all the power and common sense you've come to expect in an object-oriented language.

• Mixins. Add member functions to a class without enforcing a strict single-inheritance relationships. The before, after, and wrapped "advice" decorations can be used to modify existing functions.

• Interfaces. Classical interface pattern lets you write code that is self-documenting and forces define-time checks on code contracts.

• Member decorations. Use modifiers on class members, mixin members, or interface members to change their behavior or enforce inheritance and access semantics, or use custom decorations and reflection to amp up your own classes and reduce boilerplate.

• Define-time semantics checking. Use the virtual, abstract, and override member decorations to ensure predictable inheritance behavior, and get feedback in the form of define-time errors when implementation contracts are broken.

Getting Started

Defining Classes

Extending Classes

Using Mixins

Implementing Interfaces

Class Member Decorations

Member decorations are a key part of Typedef. They allow for the attachment of meta tags onto members during class definition. This meta information can then be used to inforce certain rules, or change the behavior of the member.

All decorations are surrounded by 2 underscores, and multiple decorations can be set on a single member.

Inheritance Decorations

The inheritance decorations are used to govern and check the inheritance semantics of your classes.

All inheritance decorations only add additional checking overhead during define time; no run-time overhead is incurred after the initial load and definition.

virtual

abstract

override

sealed

new

Accessor Decorations

readonly

static

Mixin Decorations

before

after

wrapped

Semantic Decorations

fluent

Constructor Decoration

constructor

Compatibility

Typedef will work with the following browsers:

• Chrome 7+
• Firefox 4+
• Safari 5.1+
• Opera 4+
• Internet Explorer 9+

Tests

npm install
grunt test

Special Thanks

Contributers

• Brandon Valosek @bvalosek
• Dillon Shook dshook.is

License

Copyright 2013 Brandon Valosek

Typedef is released under the MIT licenses.