ts-nested-error

ts-nested-error

Super lightweight crossplatform (browser compatible) dependency-free nested error implementation.

new NestedError(message: string, public readonly innerError?: Error)

Class that provides readonly innerError?: Error property alongside with an error callstack (as .stack property) of original error eagerly combined with itself's. Deeply nested errors form a list of callstacks and error messages that are concatenated.

Example:

    try {
        throw new Error('Connection timed out');
    } catch (err) {
        throw new NestedError(`Oh no, couldn't load file! More info in inner error`, err);
    }

This code will produce an error that when stringifed shows the following message:

NestedError: Oh no, couldn't load file! More info in inner error
    at someMethod (/path/to/code.js:line:column)
    at ...

======= INNER ERROR =======

Error: Connection timed out
    at someMethod (/path/to/code.js:line:column)
    at ...

NestedError.rethrow(message: string)

Returns a function that throws NestedError or an object of class that is derived from it with the given message. This is mostly intended to be a shorthand to create error wrapping callbacks for Promises:

import { NestedError } from 'ts-nested-error';

class DbError extends NestedError {}

database.get().then(
    data => console.log(`Hooray! data: ${data}`),
    DbError.rethrow('some database error happened') // throws instanceof DbError
);

toError(err)

Returns err itself if err instanceof Error === true, otherwise attemts to stringify it and wrap into Error object to be returned.

const err = new Error('oops');

// noop if err instanceof Error
toError(err) === err; 

// wrapped 42 into Error with warning message
(toError(42) instanceof Error) === true; 

toError('non-error value').message === `Value that is not an instance of Error was thrown: non-error value`