AssertionError and AssertionResult classes.

What is AssertionError?

Assertion Error is a module that contains two classes: AssertionError, which
is an instance of an Error, and AssertionResult which is not an instance of
Error.

These can be useful for returning from a function - if the function "succeeds"
return an AssertionResult and if the function fails return (or throw) an
AssertionError.

Both AssertionError and AssertionResult implement the Result interface:

 interface Result {
  name: "AssertionError" | "AssertionResult";
  ok: boolean;
  toJSON(...args: unknown[]): Record<string, unknown>;
}

So if a function returns AssertionResult | AssertionError it is easy to check
which one is returned by checking either .name or .ok, or check
instanceof Error.

Installation

Node.js

assertion-error is available on npm.

$ npm install --save assertion-error

Deno

assertion_error is available on
Deno.land

 import {
  AssertionError,
  AssertionResult,
} from "https://deno.land/x/[email protected]/mod.ts";