# throw-on
> Throw on console.error() & fetch
Latest version **0.8.0** (published 2023-03-11) · MIT license · 0 weekly downloads
## Install
```sh
npm install throw-on
pnpm add throw-on
yarn add throw-on
bun add throw-on
```
## Health
**Score 30/100 (F)** — status: abandoned.
Positive: has types; esm support; no vulnerabilities; high quality score.
Warnings: low downloads; pre 1.0.
Negative: abandoned; low maintenance score.
## Facts
| | |
|---|---|
| Version | 0.8.0 |
| Published | 2023-03-11 |
| First published | 2022-01-02 |
| Weekly downloads | 0 |
| License | MIT |
| TypeScript types | bundled |
| Module format | ESM + CommonJS |
| Dependencies | 0 |
| Unpacked size | 39.6 KB |
| Known vulnerabilities | 0 |
| Install scripts | no |
| GitHub stars | 24 |
| Maintainers | tkrotoff |
| Keywords | throw, console.error, React, fetch |
## Links
- npm: https://www.npmjs.com/package/throw-on
- Repository: https://github.com/tkrotoff/throw-on
- Homepage: https://github.com/tkrotoff/throw-on#readme
- Issues: https://github.com/tkrotoff/throw-on/issues
- npm.io page: https://npm.io/package/throw-on
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## Recent versions
- 0.8.0 (latest) — 2023-03-11
- 0.7.0 — 2022-11-15
- 0.6.6 — 2022-07-08
- 0.6.5 — 2022-03-03
- 0.6.4 — 2022-02-27
- 0.6.3 — 2022-02-20
- 0.6.2 — 2022-01-27
- 0.6.1 — 2022-01-26
- 0.6.0 — 2022-01-26
- 0.5.0 — 2022-01-19
- 0.4.1 — 2022-01-18
- 0.4.0 — 2022-01-18
- 0.3.0 — 2022-01-06
- 0.2.2 — 2022-01-05
- 0.2.1 — 2022-01-05
- … 2 more at https://npm.io/package/throw-on/versions
## README
# throw-on
[](https://www.npmjs.com/package/throw-on)
[](https://github.com/tkrotoff/throw-on/actions)
[](https://codeclimate.com/github/tkrotoff/throw-on/test_coverage)
[](https://bundlephobia.com/result?p=throw-on)
[](https://github.com/prettier/prettier)
[](https://github.com/airbnb/javascript)
Force console.error/warn and network requests to fail.
- Tiny: less than 100 lines of code
- No dependencies
- Fully tested
- Written in TypeScript
- Works with Node.js and browsers
- Generic: not specific to React or Jest
This is an alternative to https://github.com/ValentinH/jest-fail-on-console
## Why?
Do you have warnings like _"An update inside a test was not wrapped in act"_ or _"Can't perform a React state update on an unmounted component"_ when running or testing your React app? Are your tests performing network requests when they shouldn't?
Solution: throw whenever there is a warning (e.g. console.error/warn) or a network request that isn't mocked
- The sooner a test fails, the easier it is to fix
- Improve code quality (like an ESLint rule but at run/test time)
throw-on still displays the original console message before throwing an exception with the message `throw-on console.[METHOD]: [ORIGINAL_MESSAGE_SHORTEN]`
Result:
- before (test passes)
- after (test fails)
## Usage
### In your tests
`npm install --save-dev throw-on`
```TypeScript
// Inside jest.setup.js (Jest setupFilesAfterEnv option) for example
import {
throwOnConsole,
throwOnFetch,
throwOnXMLHttpRequestOpen
} from 'throw-on';
throwOnConsole('assert');
throwOnConsole('error');
throwOnConsole('warn');
throwOnFetch();
throwOnXMLHttpRequestOpen();
```
### In the browser
`npm install throw-on`
```TypeScript
// Inside your entry file (something like index.js, app.js, pages/_app.js)
if (process.env.NODE_ENV !== 'production') { // You probably don't want this in production
const { throwOnConsole } = await import('throw-on');
throwOnConsole('assert');
throwOnConsole('error');
throwOnConsole('warn');
}
render(, document.getElementById('app'));
```
### Make it your own
Copy-paste [throwOnConsole.ts](src/throwOnConsole.ts) and/or [throwOnFetch.ts](src/throwOnFetch.ts) and/or [throwOnXMLHttpRequestOpen.ts](src/throwOnXMLHttpRequestOpen.ts) into your source code.
### Platform support
Tested with Node.js >= 14, might work with Node.js 12.
Transpilation to ES5 (via Babel for example) is needed for non-modern browsers.
## API
```TypeScript
type Options = {
/**
* Messages to ignore (won't throw), each message to ignore can be a substring or a regex.
*
* Empty list by default.
*/
ignore?: (string | RegExp)[];
};
type ConsoleMethodName = 'assert' | 'error' | 'warn' | 'info' | 'log' | 'dir' | 'debug';
/**
* Makes console method to throw if called.
*/
function throwOnConsole(methodName: ConsoleMethodName, options: Options = {}): void;
/**
* Restores the original console method implementation.
*/
function restoreConsole(methodName: ConsoleMethodName): void;
/**
* Makes fetch to throw if called.
*/
function throwOnFetch(): void;
/**
* Restores the original fetch implementation.
*/
function restoreFetch(): void;
/**
* Makes XMLHttpRequest.open to throw if called.
*/
function throwOnXMLHttpRequestOpen(): void;
/**
* Restores the original XMLHttpRequest.open implementation.
*/
function restoreXMLHttpRequestOpen(): void;
```
## What about valid console messages?
If a `console.error()` is expected, then you should assert for it:
```TypeScript
test('should log an error', () => {
const spy = jest.spyOn(console, 'error').mockImplementation();
// ...
expect(spy).toHaveBeenCalledTimes(1);
expect(spy).toHaveBeenCalledWith('your error message');
spy.mockRestore();
});
```
## Limitations
- Be careful: it adds a line to Jest stack trace, messing up the [codeframe](https://github.com/facebook/jest/issues/8819):
```
at console. (src/throwOnConsole.ts:69:7) <===
at console.error (node_modules/@testing-library/react-hooks/lib/core/console.js:19:7)
at printWarning (node_modules/react-dom/cjs/react-dom.development.js:67:30)
at error (node_modules/react-dom/cjs/react-dom.development.js:43:5)
...
```
Use `restoreConsole()` to get the original codeframe
- Be careful: the shorten exception message does not always match the original console message (because of [React error boundary](https://reactjs.org/docs/error-boundaries.html)?)
- Libraries that console.\* exceptions [1](https://github.com/expressjs/express/blob/4.17.3/lib/application.js#L630) [2](https://github.com/expressjs/api-error-handler/blob/1.0.0/index.js#L22) introduce an infinite loop:
throw-on intercepts the console.\* call and throws an exception => the library catches the exception and console.\* it, ect.
---
_Source: https://npm.io/package/throw-on · Machine-readable twin of the npm.io package page. Health data is recomputed on every publish._