Build JavaScript applications using TypeScript

This module introduces you to the TypeScript language, why it was created, and how to use it for JavaScript development. You'll also set up a TypeScript development environment for future exercises.

JavaScript is a dynamically typed language. While this makes declaring variables easy, it can in some cases lead to unexpected results. The static type system in TypeScript enables you to describe the shape of an object, providing better documentation, and allowing TypeScript to validate that your code is working correctly. In TypeScript, declarations of namespaces, classes, properties, functions, variables, and other language entities associate types with those entities. The way that a type is formed and associated with a language entity depends on the kind of entity. This module introduces some of the available types and shows how to associate them with variables. Later modules examine how interfaces, functions, and classes use static typing.

JavaScript doesn't support interfaces so, as a JavaScript developer, you may or may not have experience with them. In TypeScript, you can use interfaces as you would in traditional object-oriented programming. You can also use interfaces to define object types and this is the primary focus of this module.

If you know how to write functions in JavaScript, you know how to write functions in TypeScript. But TypeScript adds some new capabilities to the standard JavaScript functions to make them easier to work with.

Classes in TypeScript extend the ES6 functionality by adding TypeScript-specific features like type annotations for class members, access modifiers, and the ability to specify required or optional parameters. Another benefit of using TypeScript is that you can use it to develop with classes and then compile them down to JavaScript that works across all major browsers and platforms, as needed.

Generics are code templates that you can define and reuse throughout your codebase. They provide a way to tell functions, classes, or interfaces what type you want to use when you call it.

TypeScript provides two ways to organize you code - namespaces and modules. This learn module introduces you to modules in TypeScript (referred to as external modules in previous versions.)

TypeScript provides two ways to organize code - namespaces and modules. This module explains how to organize TypeScript code using namespaces.