npm install z
const { matches } = require('z')
(x = 1) =>, (x = null) =>, (x = 'true') =>
(x = {a: 1}) =>, (x = [1, 2]) =>
(x = String) =>, (x = Boolean) =>
(x = Date) =>, (x = Person) =>
(head, tail) =>
, (a, b, c, tail) =>
, etc…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!`
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
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, 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 = []'
)
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, [y]) => x === y // stopping condition
? [x]
: [x, y],
x => x
)
}
compress([1, 1, 2, 3, 4, 4, 4]) //output: [1, 2, 3, 4]