# Classes & Constructors — JavaScript

Source: https://www.geekswithgeeks.com/en/javascript/js-classes

> Blueprints for objects, built with the class keyword.

## class and constructor

`constructor` runs automatically when you create an object with `new`, setting up its initial properties.

```js
class Dog {
  constructor(name, age) {
    this.name = name;
    this.age = age;
  }
  bark() {
    return `${this.name} says Woof!`;
  }
}
const rex = new Dog("Rex", 3);
console.log(rex.bark());
```

## Classes are syntax sugar

Under the hood, JS classes still use prototypes — `class` is a cleaner syntax over the same prototype-based system.

## The new keyword

Forgetting `new` before a class constructor throws a `TypeError` — classes can't be called like regular functions.