Property setters and getters

Our classes so far have had simple property declarations. However, for more complex scenarios, we can implement a property with a getter and a setter. When implementing getters and setters, generally, you'll need a private property to hold the property value:

• getter is a function with the property name and the get keyword at the beginning and no parameters. Generally, this will return the value of the associated private property.
• setter is a function with the same name with the set keyword at the beginning and a single parameter for the value. This will set the value of the associated private property.
• The private property is commonly named the same as the getter and setter with an underscore in front.

Let's take a look at an example:

1. Let's create getters and setters for the unitPrice property in our Product class. The setter ensures the value is not less than 0. The getter ensures null or undefined is never returned:

class Product {
  name: string;

  private _unitPrice: number;
  get unitPrice(): number {
    return this._unitPrice || 0;
  }
  set unitPrice(value: number) {
    if (value < 0) {
      value = 0;
    }
    this._unitPrice = value;
  }
}

1. Let's consume the Product class and try this out:

const table = new Product();
table.name = "Table";
console.log(table.unitPrice); 
table.unitPrice = -10;
console.log(table.unitPrice); 

If we run this, we should see two 0's in the console.