constructor and instance

Learn to create a new instance with constructor and the new operator.

What is a constructor?

A constructor is a special method that runs when a new instance is created from a class. Its name is always constructor, and it usually sets the initial properties of the instance.

class User {
  constructor(name) {
    this.name = name;
  }
}

Here this points to the new instance, and this.name adds a property to it.

The new operator

To create an instance you use the new operator: const u = new User("Alex");. This expression does the following:

Creates a new empty object.
Calls the constructor and binds this to that object.
Returns the created object.

The result, assigned to u, is an instance of the class.

Exercise Product class

Declare a Product class. Its constructor takes name and price parameters and assigns them to this.name and this.price.

Show example solution

Inside the constructor write this.name = name and this.price = price.
Example solution:
class Product {
  constructor(name, price) {
    this.name = name;
    this.price = price;
  }
}

Test yourself

What does `new User("Alex")` return?
```
new User("Alex")
```
- a class
- a method
- a property
- an instance
Show answer

an instance — Correct! The new operator returns a new instance of the class.
Create a new instance
```
const u = ____;
```
Show answer
```
const u = new User();
```
Match the concepts

constructor

initializer method
new

instance creation operator
this

points to the new instance
instance

object made from a class

Next lesson: Methods and this

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