Example of how to use decorators with typescript implementation to do pretty syntax abstract classes

abstract-class-and-methods-example.ts

function abstractMethod() {
    return function (target, propertyKey: string, descriptor: PropertyDescriptor) {
        console.log("am(): called");
        function abstractMethod() {
            throw new TypeError('It is abstract method, this error should never be thrown')
        }
        abstractMethod.__abstractMethod = true;
        descriptor.value = abstractMethod;
    }
}
function abstractClass(constructor) {
    return class AbstrctClass extends constructor {
        constructor(...args) {
            if (new.target === AbstrctClass) {
                throw new TypeError(`Cannot construct ${constructor.name} instances directly it is abstract class`);
            }
            const notImplemented = [];
            for (const method in constructor.prototype) {
                if (new.target.prototype[method].__abstractMethod) {
                    notImplemented.push(method);
                }
            }
            if (notImplemented.length) {
                throw new TypeError(`You are extending abstract class ${constructor.name}, you must implement this methods: ${notImplemented}`)
            }
            super(...args);
        }
    }
}

@abstractClass
class A {
    @abstractMethod()
    abstractM1() {}
}

// var a = new A();
// a.abstractMethod();

@abstractClass
class B extends A {
    @abstractMethod()
    abstractM2() {}
}

class C extends B {
}
// Excpect error
// TypeError: You are extending abstract class B, you must implement this methods: abstractM2,abstractM1
var c = new C();