moy-fp/src/Functor/extract.js

A functional programming library.

import curry from '../Function/curry'

/**
 * Functor f => f a -> a
 * [a] -> [a]
 */
const extract = curry(
  F => {
    switch(Object.prototype.toString.call(F)){
      case '[object Identity]': return F.value
      case '[object Maybe]': return F.value === null || F.value === undefined ? null : F.value
      case '[object IO]': return F.unsafePerformIO
      case '[object Task]': return F.fork
      case '[object Array]': return F
      default: return ;
    }
})

export default extract