What Is TypeScript and Why Use It

TypeScript is a typed version of JavaScript. It allows you to define the shape of your data and make your code more structured and predictable.

In JavaScript, you can create variables and functions without specifying what kind of data they should work with. This gives you flexibility, but it can also lead to mistakes that are harder to catch early.

For example, a function might expect a number, but receive a string instead. JavaScript will not stop you, and the error may only appear when the code runs.

TypeScript helps prevent this by allowing you to define types.

function add(a: number, b: number): number {
  return a + b;
}

In this example, both parameters and the return value are defined as numbers. If you try to pass a different type, TypeScript will show an error before the code runs.

TypeScript does not replace JavaScript. It builds on top of it.

You still write JavaScript logic, but with additional type information that improves readability and reduces unexpected errors.

After writing TypeScript code, it is compiled into regular JavaScript so it can run in environments like Node.js.

In this track, you are learning TypeScript because it is the primary language used in Nest.js. Understanding its basics will make it much easier to work with structured backend applications in the next block.