https://github.com/z-pattern-matching/z

Pattern Matching for Javascript
https://github.com/z-pattern-matching/z

functional-programming immutability pattern-matching

Last synced: about 1 month ago
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Pattern Matching for Javascript

• Host: GitHub
• URL: https://github.com/z-pattern-matching/z
• Owner: z-pattern-matching
• License: apache-2.0
• Created: 2015-09-01T14:37:18.000Z (almost 9 years ago)
• Default Branch: master
• Last Pushed: 2023-10-28T18:22:35.000Z (8 months ago)
• Last Synced: 2024-05-03T02:33:07.677Z (about 2 months ago)
• Topics: functional-programming, immutability, pattern-matching
• Language: JavaScript
• Homepage: https://z-pattern-matching.github.io/
• Size: 509 KB
• Stars: 1,719
• Watchers: 23
• Forks: 48
• Open Issues: 23
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

Lists

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README

        
# ![z](https://raw.githubusercontent.com/leonardiwagner/z/master/z-logo.png) Pattern matching for JavaScript

[![Build Status](https://travis-ci.org/z-pattern-matching/z.svg?branch=master)](https://travis-ci.org/z-pattern-matching/z)

[![Coverage Status](https://coveralls.io/repos/github/z-pattern-matching/z/badge.svg?branch=master)](https://coveralls.io/github/z-pattern-matching/z?branch=master)

[![NPM version](https://img.shields.io/npm/v/z.svg)](https://www.npmjs.com/package/z)

### Usage

- Install via npm: `npm install z`

- Require z in your code and use the matches function: `const { matches } = require('z')`

### Avaiable Patterns

- Matches by value: `(x = 1) =>, (x = null) =>, (x = 'true') =>`

- Matches by object or array: `(x = {a: 1}) =>, (x = [1, 2]) =>`

- Matches by type: `(x = String) =>, (x = Boolean) =>`

- Matches by instance: `(x = Date) =>, (x = Person) =>`

- Matches by splitting array into elements and tail `(head, tail) =>` , `(a, b, c, tail) =>`, etc…

### Examples

- **Example:** Matches by Object property

```javascript

const { matches } = require('z')

const person = { name: 'Maria' }

matches(person)(

  (x = { name: 'John' }) => console.log('John you are not welcome!'),

  (x)                    => console.log(`Hey ${x.name}, you are welcome!`)

)

//output: `Hey Maria, you are welcome!`

```

- **Example:** Matches by type or instances

```javascript

const { matches } = require('z')

const result = matches(1)(

  (x = 2)      => 'number 2 is the best!!!',

  (x = Number) => `number ${x} is not that good`,

  (x = Date)   => 'blaa.. dates are awful!'

)

console.log(result) // output: number 1 is not that good

```

- **Example:** matches Array content

> To match array content you need create multiple arguments for the match function, such as (a, b, c, tail) => {} , then each variable match each item from array. Note: last variable contains all remaining array items, formally named tail. Examples:

```javascript

const { matches } = require('z')

matches([1, 2, 3, 4, 5])(

  (a, b, c, tail) => 'a = 1, b = 2, c = 3, tail = [4, 5]'  

)

matches([1, 2])(

  (a, tail) => 'a = 1, b = [2]'  

)

matches([1])(

  (a, b,  tail)       => 'Will not match here',

  (a = 2, tail = [])  => 'Will not match here',

  (a = 1, tail = [])  => 'Will match here, tail = []'

)

```

- **Example:** Powerful recursive code which will remove sequential repeated items from Array.

> Can be mind blowing if it’s the first time you meet pattern matching, but you are gonna understand it!

```javascript

const { matches } = require('z')

const compress = (numbers) => {

  return matches(numbers)(

    (x, y, xs) => x === y

      ? compress([x].concat(xs))

      : [x].concat(compress([y].concat(xs))),

    (x, [y]) => x === y // stopping condition

      ? [x]

      : [x, y],

    x => x

  )

}

compress([1, 1, 2, 3, 4, 4, 4]) //output: [1, 2, 3, 4]

```

### License

[Apache 2.0][apache-license]

[apache-license]:./LICENSE