[![Node](https://img.shields.io/badge/-Node.js-808080?logo=node.js&colorA=404040&logoColor=66cc33)](https://www.npmjs.com/package/set-error-props) [![Browsers](https://img.shields.io/badge/-Browsers-808080?logo=firefox&colorA=404040)](https://unpkg.com/set-error-props?module) [![TypeScript](https://img.shields.io/badge/-Typed-808080?logo=typescript&colorA=404040&logoColor=0096ff)](/src/main.d.ts) [![Codecov](https://img.shields.io/badge/-Tested%20100%25-808080?logo=codecov&colorA=404040)](https://codecov.io/gh/ehmicky/set-error-props) [![Minified size](https://img.shields.io/bundlephobia/minzip/set-error-props?label&colorA=404040&colorB=808080&logo=webpack)](https://bundlephobia.com/package/set-error-props) [![Mastodon](https://img.shields.io/badge/-Mastodon-808080.svg?logo=mastodon&colorA=404040&logoColor=9590F9)](https://fosstodon.org/@ehmicky) [![Medium](https://img.shields.io/badge/-Medium-808080.svg?logo=medium&colorA=404040)](https://medium.com/@ehmicky) Properly update an error's properties. # Features - Prevents overriding [error core properties](#error-core-properties) (`name`, `message`, etc.) - Protects against [prototype pollution](#prototype-pollution) - Prevents overriding [existing properties](#overriding-protection) - [Copies](#error-copy) another error's properties - Can set properties as [non-enumerable](#non-enumerable-properties) - Preserves properties [descriptors](#descriptors) (`enumerable`, `writable`, `configurable`, `get`/`set`) - [Exception-safe](#exception-safety): this only throws syntax errors - Strict [TypeScript typing](/src/main.d.ts) of the return value # Example ```js import setErrorProps from 'set-error-props' const error = new Error('one') setErrorProps(error, { prop: true, message: 'two' }) console.log(error.prop) // true console.log(error.message) // 'one': message is readonly ``` # Install ```bash npm install set-error-props ``` This package works in both Node.js >=18.18.0 and [browsers](https://raw.githubusercontent.com/ehmicky/dev-tasks/main/src/browserslist). This is an ES module. It must be loaded using [an `import` or `import()` statement](https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c), not `require()`. If TypeScript is used, it must be configured to [output ES modules](https://www.typescriptlang.org/docs/handbook/esm-node.html), not CommonJS. # API ## setErrorProps(error, props, options?) `error` `Error | object`\ `props` `Error | object`\ `options` [`Options?`](#options)\ _Return value_: `Error` Assigns `props` to `error`, then returns `error`. ### Options #### soft _Type_: `boolean`\ _Default_: `false` Prevents [overriding](#overriding-protection) existing properties. # Usage ## Error core properties ```js const error = new Error('one') setErrorProps(error, { message: 'two' }) console.log(error.message) // 'one' ``` ## Prototype pollution ```js const error = new Error('one') setErrorProps(error, { toString: () => 'injected' }) console.log(error.toString()) // 'Error: one' console.log(Error.prototype.toString()) // 'Error' ``` ## Overriding protection ```js const error = new Error('message') error.one = true setErrorProps(error, { one: false, two: true }, { soft: true }) console.log(error.one) // true console.log(error.two) // true ``` ## Error copy ```js const error = new Error('one') const secondError = new Error('two') secondError.prop = true setErrorProps(error, secondError) console.log(error.message) // 'one' console.log(error.prop) // true ``` ## Non-enumerable properties ```js const error = new Error('message') // Properties that start with `_` are not enumerable setErrorProps(error, { _one: true, two: true }) console.log(error._one) // true console.log(error.two) // true console.log(Object.keys(error)) // ['two'] console.log(error) // Prints `two` but not `_one` ``` ## Descriptors ```js const error = new Error('message') Object.defineProperty(error, 'prop', { value: false, enumerable: false, writable: true, configurable: true, }) setErrorProps(error, { prop: true }) console.log(error.prop) // true console.log(Object.getOwnPropertyDescriptor(error, 'prop').enumerable) // false ``` ## Exception safety ```js const error = new Proxy(new Error('message'), { set: () => { throw new Error('example') }, defineProperty: () => { throw new Error('example') }, }) setErrorProps(error, { prop: true }) // This does not throw ``` # Related projects - [`modern-errors`](https://github.com/ehmicky/modern-errors): Handle errors in a simple, stable, consistent way - [`error-custom-class`](https://github.com/ehmicky/error-custom-class): Create one error class - [`error-class-utils`](https://github.com/ehmicky/error-class-utils): Utilities to properly create error classes - [`error-serializer`](https://github.com/ehmicky/error-serializer): Convert errors to/from plain objects - [`normalize-exception`](https://github.com/ehmicky/normalize-exception): Normalize exceptions/errors - [`is-error-instance`](https://github.com/ehmicky/is-error-instance): Check if a value is an `Error` instance - [`set-error-class`](https://github.com/ehmicky/set-error-class): Properly update an error's class - [`set-error-message`](https://github.com/ehmicky/set-error-message): Properly update an error's message - [`wrap-error-message`](https://github.com/ehmicky/wrap-error-message): Properly wrap an error's message - [`set-error-stack`](https://github.com/ehmicky/set-error-stack): Properly update an error's stack - [`merge-error-cause`](https://github.com/ehmicky/merge-error-cause): Merge an error with its `cause` - [`error-cause-polyfill`](https://github.com/ehmicky/error-cause-polyfill): Polyfill `error.cause` - [`handle-cli-error`](https://github.com/ehmicky/handle-cli-error): 💣 Error handler for CLI applications 💥 - [`log-process-errors`](https://github.com/ehmicky/log-process-errors): Show some ❤ to Node.js process errors - [`error-http-response`](https://github.com/ehmicky/error-http-response): Create HTTP error responses - [`winston-error-format`](https://github.com/ehmicky/winston-error-format): Log errors with Winston # Support For any question, _don't hesitate_ to [submit an issue on GitHub](../../issues). Everyone is welcome regardless of personal background. We enforce a [Code of conduct](CODE_OF_CONDUCT.md) in order to promote a positive and inclusive environment. # Contributing This project was made with ❤️. The simplest way to give back is by starring and sharing it online. If the documentation is unclear or has a typo, please click on the page's `Edit` button (pencil icon) and suggest a correction. If you would like to help us fix a bug or add a new feature, please check our [guidelines](CONTRIBUTING.md). Pull requests are welcome!