Native Pattern Matching for Javascript
The pattern matching is basically a switch on steroids, you can create powerful conditions such based on Object properties or Array content without manipulating the Object or Array itself. That amount of power leads you write functional, immutable, and expressive code instead imperative, which reduces a lot of complexity and bugs.
Usage:
- Install via npm:
npm install z - Require z in your code and use the matches function:
const { matches } = require('z') - Support this project! Star
Example: Matches by Object property
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
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 goodExample: 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:
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, tail = [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!
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, xs) => x // stopping condition
)
}
compress([1, 1, 2, 3, 4, 4, 4]) //output: [1, 2, 3, 4]Benefits
✔️ Conditionals without array or object manipulation
✔️ Write functional declarative code instead imperative
✔️ Reduces code complexity and bugs
✔️ Code reuse via recursion
patterns
Available 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 spiting array into elements and tail
(head, tail) =>,(a, b, c, tail) =>, etc…