ES2015 does not have Java-style classes with built-in affordances for your desired design pattern. However, it has some options which may be helpful, depending on exactly what you are trying to accomplish.
If you would like a class that cannot be constructed, but whose subclasses can, then you can use new.target:
class Abstract {
constructor() {
if (new.target === Abstract) {
throw new TypeError("Cannot construct Abstract instances directly");
}
}
}
class Derived extends Abstract {
constructor() {
super();
// more Derived-specific stuff here, maybe
}
}
const a = new Abstract(); // new.target is Abstract, so it throws
const b = new Derived(); // new.target is Derived, so no error
For more details on new.target, you may want to read this general overview of how classes in ES2015 work: http://www.2ality.com/2015/02/es6-classes-final.html
If you're specifically looking for requiring certain methods be implemented, you can check that in the superclass constructor as well:
class Abstract {
constructor() {
if (this.method === undefined) {
// or maybe test typeof this.method === "function"
throw new TypeError("Must override method");
}
}
}
class Derived1 extends Abstract {}
class Derived2 extends Abstract {
method() {}
}
const a = new Abstract(); // this.method is undefined; error
const b = new Derived1(); // this.method is undefined; error
const c = new Derived2(); // this.method is Derived2.prototype.method; no error
