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					71 lines
				
				2.8 KiB
			| 
											3 years ago
										 | # process-warning
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|  | 
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|  |  | ||
|  | [](https://www.npmjs.com/package/process-warning) | ||
|  | [](https://snyk.io/test/github/fastify/process-warning) | ||
|  | [](https://standardjs.com/) | ||
|  | 
 | ||
|  | A small utility for generating consistent warning objects across your codebase. | ||
|  | It also exposes a utility for emitting those warnings, guaranteeing that they are issued only once. | ||
|  | 
 | ||
|  | This module is used by the [Fastify](https://fastify.io) framework and it was called `fastify-warning` prior to version 1.0.0. | ||
|  | 
 | ||
|  | ### Install
 | ||
|  | 
 | ||
|  | ``` | ||
|  | npm i process-warning | ||
|  | ``` | ||
|  | 
 | ||
|  | ### Usage
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|  | 
 | ||
|  | The module exports a builder function that returns a utility for creating warnings and emitting them. | ||
|  | 
 | ||
|  | ```js | ||
|  | const warning = require('process-warning')() | ||
|  | ``` | ||
|  | 
 | ||
|  | #### Methods
 | ||
|  | 
 | ||
|  | ``` | ||
|  | warning.create(name, code, message) | ||
|  | ``` | ||
|  | 
 | ||
|  | - `name` (`string`, required) - The error name, you can access it later with `error.name`. For consistency, we recommend prefixing module error names with `{YourModule}Warning` | ||
|  | - `code` (`string`, required) - The warning code, you can access it later with `error.code`. For consistency, we recommend prefixing plugin error codes with `{ThreeLetterModuleName}_`, e.g. `FST_`. NOTE: codes should be all uppercase. | ||
|  | - `message` (`string`, required) - The warning message. You can also use interpolated strings for formatting the message. | ||
|  | 
 | ||
|  | The utility also contains an `emit` function that you can use for emitting the warnings you have previously created by passing their respective code. A warning is guaranteed to be emitted only once. | ||
|  | 
 | ||
|  | ``` | ||
|  | warning.emit(code [, a [, b [, c]]]) | ||
|  | ``` | ||
|  | 
 | ||
|  | - `code` (`string`, required) - The warning code you intend to emit. | ||
|  | - `[, a [, b [, c]]]` (`any`, optional) - Parameters for string interpolation. | ||
|  | 
 | ||
|  | ```js | ||
|  | const warning = require('process-warning')() | ||
|  | warning.create('FastifyWarning', 'FST_ERROR_CODE', 'message') | ||
|  | warning.emit('FST_ERROR_CODE') | ||
|  | ``` | ||
|  | 
 | ||
|  | How to use an interpolated string: | ||
|  | ```js | ||
|  | const warning = require('process-warning')() | ||
|  | warning.create('FastifyWarning', 'FST_ERROR_CODE', 'Hello %s') | ||
|  | warning.emit('FST_ERROR_CODE', 'world') | ||
|  | ``` | ||
|  | 
 | ||
|  | The module also exports an `warning.emitted` [Map](https://developer.mozilla.org/it/docs/Web/JavaScript/Reference/Global_Objects/Map), which contains all the warnings already emitted. Useful for testing. | ||
|  | ```js | ||
|  | const warning = require('process-warning')() | ||
|  | warning.create('FastifyWarning', 'FST_ERROR_CODE', 'Hello %s') | ||
|  | console.log(warning.emitted.get('FST_ERROR_CODE')) // false | ||
|  | warning.emit('FST_ERROR_CODE', 'world') | ||
|  | console.log(warning.emitted.get('FST_ERROR_CODE')) // true | ||
|  | ``` | ||
|  | 
 | ||
|  | ## License
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|  | 
 | ||
|  | Licensed under [MIT](./LICENSE). |