TypeScript constructor - environmental error

Question

How to create a constructor in TypeScript?

I looked at a bunch of manuals, but the syntax should have changed. Here is my last attempt:

car.d.ts

declare class Car {
    constructor(public engine: string) {
        this.engine = engine + "foo";
    }
}

Mistake:

Implementation cannot be invoked in surrounding contexts.

Answer 1

Using declare, you determine the type of class. The type is defined only and should not have an implementation, so declareyou must delete it. Then it compiles fine.

class Car {
    constructor(public engine: string) {
        this.engine = engine + "foo";
    }
}

However, this code compiles into:

var Car = (function () {
    function Car(engine) {
        this.engine = engine;
        this.engine = engine + "foo";
    }
    return Car;
})();

which sets the property twice engine.

This is probably not what you intended, so the property engineshould be defined in the class, not in the constructor.

class Car {

    public engine: string;

    constructor(engine: string) {
        this.engine = engine + "foo";
    }
}

Edit:

, declare, , .d.ts . .ts, , JavaScript.

2:

declare class Car {

    public engine;

    constructor(engine: string);
}