Cloneable.ts

import { isUndefined } from "lodash";

export abstract class Cloneable<T> {
  public clone(newValues: Partial<T> = {}): T {
    const clone = new (this.constructor as new () => T)();
    const newValuesWithNestedClones = Object.getOwnPropertyNames(clone)
      .reduce((partial, propertyName) => {
        const property = Object.getOwnPropertyDescriptor(clone, propertyName) as PropertyDescriptor;
        const isCloneable = property.value instanceof Cloneable;
        const isNotProvided = isUndefined(
          Object.getOwnPropertyDescriptor(partial, propertyName),
        );

        if (isCloneable && isNotProvided) {
          // tslint:disable-next-line:no-unsafe-any
          partial[propertyName as keyof T] = property.value.clone();
        }

        return partial;
      },      newValues);

    return Object.assign(clone, this, newValuesWithNestedClones);
  }

  public cloneWith(newValues: Partial<T>): T {
    return this.clone(newValues);
  }
}

generic-clone-function.ts

function clone<T>(instance: T): T {
    const copy = new (instance.constructor as { new (): T })();
    Object.assign(copy, instance);
    return copy;
}