on-error-resume-next

on-error-resume-next

Run a function, synchronously or asynchronously, and ignore errors.

The name come from Visual Basic. The original On Error Resume Next statement is considered a bad error handling practice.

Although the perception of the feature is negative, when scoped and used responsibly, it can become a very helpful utility function.

Usage

onErrorResumeNext will return the result if it is a success. For example,

import onErrorResumeNext from 'on-error-resume-next';

const text = '{"hello":"World!"}';
const parsed = onErrorResumeNext(() => JSON.parse(text));

expect(parsed).toEqual({ hello: 'World!' });

Otherwise, it will return undefined,

const parsed = onErrorResumeNext(() => JSON.parse('<xml />'));

expect(parsed).toBeUndefined();

When using onErrorResumeNext, please be responsible and fully understand the impact of ignoring errors.

Asynchronous using async/await

onErrorResumeNext will capture both exceptions (synchronous) and rejections (asynchronous). It is recommended to pair up with await keyword to handle both cases in the same way.

const res = await onErrorResumeNext(() => fetch('/health'));

expect(res).toBeUndefined();

The code is for elaboration only, the better expectation should be expect(res).resolves.toBeUndefined().

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