Is there an equivalent to “sealed” or “final” in TypeScript?

Question

I\'m trying to implement a method in a super class that should be available for use, but not changeable, in sub classes. Consider this:

export abstract clas         


        

Answer 1

Example of implementation hack of 'sealed method' as readonly property of type function which throws compiler error when attempting to override in extended class:

abstract class BaseClass {
    protected element: JQuery;
    constructor(element: JQuery) {
        this.element = element;
    }
    readonly public dispose = (): void => {
        this.element.remove();
    }
}

class MyClass extends BaseClass {
    constructor(element: JQuery) {
        super(element);
    }
    public dispose(): void { } // Compiler error: "Property 'dispose' in type 'MyClass' is not assignable to the same property in base type 'BaseClass'"
}

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TypeScript 2.0 supports "final" classes through using of private constructor:

class A {
    private constructor(){}
}

class B extends A{} //Cannot extend a class 'A'. Class constructor is marked as private.ts(2675)