Publish to npm The Publishing section explains how to publish your declaration files to an npm package, and shows how to manage your dependent packages.

Merging Namespaces with Classes This gives the user a way of describing inner classes. class Album { label: Album.AlbumLabel; } namespace Album { export class AlbumLabel { } } The visibility rules for merged members is the same as described in the ‘Merging Namespaces’ section, so we must export the AlbumLabel class for the merged class to see it. The end result is a class managed inside of another class. You can also use namespaces to add more static members to an existing class. In additi

Boolean The most basic datatype is the simple true/false value, which JavaScript and TypeScript call a boolean value. let isDone: boolean = false;

Using Modules Just like namespaces, modules can contain both code and declarations. The main difference is that modules declare their dependencies. Modules also have a dependency on a module loader (such as CommonJs/Require.js). For a small JS application this might not be optimal, but for larger applications, the cost comes with long term modularity and maintainability benefits. Modules provide for better code reuse, stronger isolation and better tooling support for bundling. It is also worth

Optional Properties Not all properties of an interface may be required. Some exist under certain conditions or may not be there at all. These optional properties are popular when creating patterns like “option bags” where you pass an object to a function that only has a couple of properties filled in. Here’s an example of this pattern: interface SquareConfig { color?: string; width?: number; } function createSquare(config: SquareConfig): {color: string; area: number} { let newSquare = {c

TypeScriptCompileBlocked If you are using a different build tool to build your project (e.g. gulp, grunt , etc.) and VS for the development and debugging experience, set <TypeScriptCompileBlocked>true</TypeScriptCompileBlocked> in your project. This should give you all the editing support, but not the build when you hit F5.

Publicize your declaration file After publishing your declaration file with your package, make sure to add a reference to it in the DefinitelyTyped repo external package list. Adding this will allow search tools to know that your package provides its own declarations.

Array TypeScript, like JavaScript, allows you to work with arrays of values. Array types can be written in one of two ways. In the first, you use the type of the elements followed by [] to denote an array of that element type: let list: number[] = [1, 2, 3]; The second way uses a generic array type, Array<elemType>: let list: Array<number> = [1, 2, 3];

Ambient enums Ambient enums are used to describe the shape of already existing enum types. declare enum Enum { A = 1, B, C = 2 } One important difference between ambient and non-ambient enums is that, in regular enums, members that don’t have an initializer are considered constant members. For non-const ambient enums member that does not have initializer is considered computed.

The JSX result type By default the result of a JSX expression is typed as any. You can customize the type by specifying the JSX.Element interface. However, it is not possible to retrieve type information about the element, attributes or children of the JSX from this interface. It is a black box.