Inherit from Error breaks `instanceof` check in TypeScript

Question

Can someone explain me why the error instanceof CustomError part of below code is false ?

class CustomError extends Error {}

cons         


        

Answer 1

Turns out an change has been introduced in TypeScript@2.1 that breaks this pattern. The whole breaking change is described here.

In general it seems it's too complicated/error to even go with this direction.

Probably better to have own error object and keeps some original Error as an property:

class CustomError {
    originalError: Error;

    constructor(originalError?: Error) {
        if (originalError) {
            this.originalError = originalError
        }
    }
}

class SpecificError extends CustomError {}

const error = new SpecificError(new Error('test'));

console.log(error instanceof CustomError); // true
console.log(error instanceof SpecificError); // true