Chapter 2: Leveling Up with TypeScript

Now that we learned the basics of JavaScript, we could theoretically dive right into writing our application. However, JavaScript as a language has a central problem—it does not come with type checking. For example, there is nothing preventing you from trying to add two objects except the fact that—well—your application will crash and burn.

In general, one of the most common error sources are what can be described as type errors: a certain kind of value was used where a different kind of value was expected. This could be due to simple typos, a failure to understand how to use a library correctly, incorrect assumptions about runtime behavior and more.

The goal of TypeScript is to provide static type checking for JavaScript programs—in other words, TypeScript provides you with tooling that runs before your code is executed (static) and ensures that the types of the program are correct (type checking).