forked from lix-project/lix-website
144 lines
2.9 KiB
Markdown
144 lines
2.9 KiB
Markdown
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# zwitch
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[![Build][build-badge]][build]
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[![Coverage][coverage-badge]][coverage]
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[![Downloads][downloads-badge]][downloads]
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[![Size][size-badge]][size]
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Handle values based on a property.
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## Install
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[npm][]:
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```sh
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npm install zwitch
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```
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## Use
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```js
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var zwitch = require('zwitch')
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var handle = zwitch('type')
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handle.invalid = invalid
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handle.unknown = unknown
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handle.handlers.alpha = handle
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handle({type: 'alpha'})
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```
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Or, with a `switch` statement:
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```javascript
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function handle(value) {
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var fn
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if (!value || typeof value !== 'object' || !('type' in value)) {
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fn = invalid
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} else {
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switch (value.type) {
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case 'alpha':
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fn = handle
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break
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default:
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fn = unknown
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break
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}
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}
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return fn.apply(this, arguments)
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}
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handle({type: 'alpha'})
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```
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## API
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### `zwitch(key[, options])`
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Create a functional switch, based on a `key` (`string`).
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###### `options`
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Options can be omitted and added later to `one`.
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* `handlers` (`Object.<Function>`, optional)
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— Object mapping values to handle, stored on `one.handlers`
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* `invalid` (`Function`, optional)
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— Handle values without `key`, stored on `one.invalid`
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* `unknown` (`Function`, optional)
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— Handle values with an unhandled `key`, stored on `one.unknown`
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###### Returns
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`Function` — See [`one`][one].
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#### `one(value[, rest...])`
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Handle one value. Based on the bound `key`, a respective handler will be
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invoked.
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If `value` is not an object, or doesn’t have a `key` property, the special
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“invalid” handler will be invoked.
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If `value` has an unknown `key`, the special “unknown” handler will be invoked.
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All arguments, and the context object, are passed through to the [handler][],
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and it’s result is returned.
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#### `one.handlers`
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Map of [handler][]s (`Object.<string, Function>`).
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#### `one.invalid`
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Special [`handler`][handler] invoked if a value doesn’t have a `key` property.
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If not set, `undefined` is returned for invalid values.
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#### `one.unknown`
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Special [`handler`][handler] invoked if a value does not have a matching
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handler.
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If not set, `undefined` is returned for unknown values.
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### `function handler(value[, rest...])`
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Handle one value.
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## Related
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* [`mapz`](https://github.com/wooorm/mapz)
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— Functional map
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## License
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[MIT][license] © [Titus Wormer][author]
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<!-- Definitions -->
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[build-badge]: https://img.shields.io/travis/wooorm/zwitch.svg
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[build]: https://travis-ci.org/wooorm/zwitch
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[coverage-badge]: https://img.shields.io/codecov/c/github/wooorm/zwitch.svg
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[coverage]: https://codecov.io/github/wooorm/zwitch
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[downloads-badge]: https://img.shields.io/npm/dm/zwitch.svg
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[downloads]: https://www.npmjs.com/package/zwitch
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[size-badge]: https://img.shields.io/bundlephobia/minzip/zwitch.svg
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[size]: https://bundlephobia.com/result?p=zwitch
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[npm]: https://docs.npmjs.com/cli/install
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[license]: license
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[author]: https://wooorm.com
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[one]: #onevalue-rest
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[handler]: #function-handlervalue-rest
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