redp

Red Phosphorus - Pattern Match Library for ES2015 Era

example

import {match, when} from 'redp'

// create function to calculate expression tree
const calc = match.fn({
  [when({type: 'binary', operator: '+'})]: ({left, right}) => calc(left) + calc(right),
  [when({type: 'binary', operator: '*'})]: ({left, right}) => calc(left) * calc(right),
  [when({type: 'unary' , operator: '-'})]: ({value}) => -calc(value),
  [when({type: 'number'})]               : ({value}) => value,
})

// -100 + 200 ==> 100
console.log(calc({
  type: 'binary',
  operator: '+',
  left: {
    type: 'unary',
    operator: '-',
    value: {
      type: 'number',
      value: 100,
    },
  },
  right: {
    type: 'number',
    value: 200,
  },
}))

You could be look for more examples in example/ and test/.

install

$ npm install --save redp

API

import {match, when, Pattern} from 'redp'

match(value, pattern)

Shortcut to match.fn(pattern)(value).

match.fn(patterns)

Create new function to match patterns. patterns should be an Object. Its keys should be created by when function. Returned function accept one argument then try to match patterns. Matching some pattern, return it. If not, return undefined.

when(pattern)

Create pattern key from pattern. pattern is either some javascript value ("string" or true or /regexp/ or (arrow) => func or ...) or Pattern.* function's result. If pattern is some javascript value, it is passed to Pattern.from.

Pattern key is not reusable. If you want to reuse pattern, you could use Pattern.from.

when.and(...patterns)

Shortcut to when(Pattern.and(...patterns)).

when.or(...patterns)

Shortcut to when(Pattern.or(...patterns)).

Pattern

This is a factory for pattern object.

export const Pattern = {
  // Wild card pattern. It can match all values.
  _: ...,

  // Rest pattern. It can match no items or some rest items of array (cannot object!).
  rest: ...,

  // Create pattern object from `object`.
  from(object) {
    // If `object` is pattern object already, return `object`.
    // If `object` is a `RegExp`, create regexp pattern.
    // If `object` is an `Array`, create array pattern.
    // If `object` is a javascript object, create object pattern.
    // If `object` is a function, create condition pattern.
    // Otherwise, create value pattern.
    ...
  },

  // Create regexp pattern.
  regexp(regexp) { ... },

  // Create array pattern.
  array(array) { ... },

  // Create object pattern.
  object(object) { ... },

  // Create condition pattern.
  condition(predicate) { ... },

  // Create value pattern.
  value(value) { ... },

  // Create 'and' pattern.
  and(...patterns) { ... },

  // Create 'or' pattern.
  or(...patterns) { ... },

  // If `object` is pattern object, return `true`,
  // otherwise return `false`.
  is(object) { ... },
}

note

This library uses ES2015 Symbol and Map. If you want to run this on not ES2015 environment, you can try to use some polyfills. (However, it is not tested. I'm waiting your pull-request)

license

MIT License: http://makenowjust.mit-license.org/2016

(C) 2016 TSUYUSATO Kitsune