What are the differences between throwing error and throwing function with error prototype

Question

I saw a very special (and weird) error handling code, which goes like this:

function SomeError(name, message) {
    this.name = name;
    this.message = message;
    this.stack = (new Error()).stack;
}
SomeError.prototype = Object.create(Error.prototype);

On promise catch:

promise.catch(e => {
    throw new SomeError('someName', e.message);
});

My question:
Is there any reasonable cause to make it this way?
I thought of handling this like:

promise.catch(e => {
    e.name = 'my error name';
    throw new Error(e);
});

Answer 1

Because it allows you to fine grain the catching:

 // Somewhere up the promise chain:
 .catch(error => {
    if(error instanceof SomeError) {
      // Handle this specific case
    } else { /* handle other cases */}
  });

The code that defines SomeError could be rewritten as the following class which makes clear what it is doing:

 class SomeError extends Error {}

It basically just creates a subclass that does nothing.