Introduction to TypeScript

A basic introduction to TypeScript. Functionalities, key concepts, and benefits.

Introduction to TypeScript

What is TypeScript?

TypeScript is an open-source, object-oriented programming language designed by Microsoft in 2012 under the Apache 2 license. It is a statically and strongly typed language that serves as a syntactic superset of JavaScript. By compiling to JavaScript, TypeScript extends the functionality of JavaScript by adding features such as data types, classes, and object-oriented elements like inheritance and generics. TypeScript is widely used by large industries including Microsoft, Slack, and Medium to develop scalable applications for both the server-side and client-side of JavaScript applications.

What is a Superset?

Let's take a moment to recall our math class. In mathematics, an element X is considered a superset of another element Y if it contains all the elements of Y. For example, if we have set X = { 1, 2, 3, 4, 5 } and set Y = { 2, 4, 5 }, we can say that set X is a superset of set Y, but we cannot say the same for set Y. Now, relating this to TypeScript, it means that every existing JavaScript code is also valid TypeScript code.

Why was TypeScript created?

Writing JavaScript can sometimes be challenging, particularly as projects grow in size. While weakly typed programming languages like JavaScript have their merits, such as fast development and simplicity, these benefits can become detrimental to a project as it expands.

TypeScript was developed to address the limitations of JavaScript when building large-scale applications. Many JavaScript applications consist of hundreds or even thousands of files, and making changes to a single file can have a ripple effect that impacts other files. Validating connections between different parts of the project can be time-consuming. By using a type-checked language like TypeScript, you can save time and receive instant feedback during development.

Benefits of TypeScript

  1. Easy debugging: TypeScript integrates fully with your IDE, enabling you to easily identify bugs in your codebase. When you make changes to a file, the IDE provides real-time feedback on other files that are dependent on those changes, helping you identify and fix issues efficiently.

  2. Static typing: TypeScript allows you to define and check types for variables, arguments, and parameters at compile time. For example, if you create a function that accepts a number as a parameter, TypeScript prevents you from passing a different type, providing an early error notification.

  3. Support for latest JavaScript features: TypeScript supports the latest JavaScript features such as arrow functions, optional chaining, and destructuring.

  4. Type inference: Based on usage, TypeScript can infer the data types for variables in your code, reducing the need for explicit type annotations and helping the compiler provide types where they were not explicitly defined.

Features of TypeScript

TypeScript is essentially JavaScript but with additional features that are not present in JavaScript. However, TypeScript compiles down to JavaScript code. Some notable features of TypeScript include:

  • Classes: TypeScript fully supports the class keyword, allowing you to define and work with classes, which are templates or blueprints for objects.

  • Interfaces: Interfaces in TypeScript enforce specific properties on objects, providing a way to define custom data types.

  • Generics: Generics enable you to create reusable code that can work with multiple types of data. They allow you to write code that is independent of specific types.

  • Type Inference: TypeScript can infer the types of variables when they are defined. In many cases, explicit type annotations are not required.

  • Tuples: Tuples are typed arrays with a predefined length and a specific type for each index.

  • Advanced Types: TypeScript offers advanced types to handle more complex relationships. You can specify that a value can have several types or combine multiple types into a single type, among other powerful features.

  • Enums: Enums in TypeScript are named sets of constants, which can be based on either numbers or strings.

  • Decorators: Decorators are a design pattern that enhances the functionality of class declarations, methods, accessors, properties, or parameters. They are denoted by the @decorator_expression syntax and provide additional runtime information.


Having worked with TypeScript for the past two years, I have experienced significantly fewer bugs in production compared to JavaScript. TypeScript makes it easier to maintain large codebases while retaining the flexibility of JavaScript. The ability to configure TypeScript's features adds to its overall appeal and makes it even more impressive.