Typescript throws error when declearing a variable as this.x = x

Question

I got a class and a constructor in it. The constructor got a value x as a parameter and I want to declare a variable for the class with

this.x = x 

but typescript throws an error:

TS2339: Property 'x' does not exist in type 'myClass'

Does anyone know how to solve this problem without declaring every single variable extra like "private x: number;" --> "this.x = x"

Answer 1

If you have a constructor parameter, you can just declare an access modifier to make it a field, You don't even need to perform the assignment (typescript will do it for you)

class C {
    constructor(public x: number) {} // can also be private or protected instead of public
    m() {
        this.x = 10;
    }
}
new C(1).x // ok, x is declared and is 1