How to declare a function that throws an error in Typescript

Question

In Java I would declare a function like this:

public boolean Test(boolean test) throws Exception {
  if (test == true)
    return false;
  throw new Excepti         


        

Answer 1

You could treat JavaScript's Error as Java's RuntimeException (unchecked exception). You can extend JavaScript's Error but you have to use Object.setPrototypeOf to restore the prototype chain because Error breaks it. The need for setPrototypeOf is explained in this answer too.

export class AppError extends Error {
    code: string;

    constructor(message?: string, code?: string) {
        super(message);  // 'Error' breaks prototype chain here
        Object.setPrototypeOf(this, new.target.prototype);  // restore prototype chain
        this.name = 'AppError';
        this.code = code;
    }
}