> For the complete documentation index, see [llms.txt](https://notes.danfitz.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://notes.danfitz.com/javascript/typescript-developers-guide/h-building-functionality-with-classes.md).

# Building Functionality With Classes

## Access Modifiers

TypeScript gives you the ability to apply access modifiers to your class's properties or methods:

* `public`
  * By default, all properties and methods have `public` access: the method and property can be accessed from anywhere any time.
* `private`
  * Can only be called by *other methods* in that same class
* `protected`
  * Can be called by others methods in the same class *or* child classes' methods

Please refer to the C# Intermediate notes to learn more!

**Pro tip**: An easy way to initialize fields in your constructor is to use the `public` modifier.

```ts
class Car {
  constructor(public color: string) {}
}

const car = new Car('red');
console.log(car.color); // red
```

## Why Classes Matter

Just like interfaces, in TypeScript, classes are one of the main tools we use to ensure strong code reuse!