Understanding Valuators in TypeScript

A Valuator is an object that can be used to evaluate the value of a property or a set of properties. In other words, it's an object that knows how to calculate the value of something.

In TypeScript, a Valuator is used to determine the type of a property or a set of properties. It's used in conjunction with the `type` keyword to specify the type of a property or a set of properties.

Here's an example:
```
interface Person {
name: string;
age: number;
}

class Employee extends Person {
salary: number;
}

function getEmployee(employee: Employee): Employee {
return employee; // returns an instance of Employee
}

let person: Person = { name: "John", age: 30 };
let employee: Employee = getEmployee(person);
console.log(employee.salary); // prints 0
```
In this example, the `Person` interface has two properties: `name` and `age`. The `Employee` class extends the `Person` interface and adds a new property called `salary`. The `getEmployee` function takes an instance of `Employee` as an argument and returns an instance of `Employee`.

The `valuator` keyword is used to specify the type of the `salary` property in the `Employee` class. In this case, the type of the `salary` property is `number`.

Without the `valuator` keyword, the type of the `salary` property would be inferred as `any`, which means it could be any type of value. By using the `valuator` keyword, we can explicitly specify the type of the property and ensure that it's always a number.

In summary, a Valuator is an object that knows how to calculate the type of a property or a set of properties. It's used in conjunction with the `type` keyword to specify the type of a property or a set of properties in TypeScript.