Creating a standard duplicate function in TypeScript

Is there a way in TypeScript for a class to reference its constructor in a manner that functions correctly when it is extended by another class?

abstract class Base<T> {
  constructor(readonly value: T) {}

  abstract getName(): string;

  clone() {
    const Cls = this.constructor;
    return new Cls(this.value);
  }
}

In the above code snippet, Cls is assigned the type of Function, resulting in a compiler error stating: "Cannot use 'new' with an expression whose type lacks a call or construct signature."

Answer №1

Typescript has a unique approach when it comes to constructors since it does not strictly enforce types, using Function. This means that if a constructor is not defined, it cannot be called with new.

To address this issue, one simple solution is to utilize type assertion as shown below:

abstract class Base<T> {
    constructor(readonly value: T) { }

    abstract getName(): string;

    clone() {
        // By using polymorphic this, we ensure the return type is accurate in derived types
        const Cls = this.constructor as new (value: T) => this;
        return new Cls(this.value);
    }
}

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