crocks/helpers/tap.js

A collection of well known Algebraic Datatypes for your utter enjoyment.

/** @license ISC License (c) copyright 2017 original and current authors */
/** @author Ian Hofmann-Hicks (evil) */

var curry = require('../core/curry')
var compose = require('../core/compose')
var isFunction = require('../core/isFunction')

var constant = function (x) { return function () { return x; }; }

// tap : (a -> b) -> a -> a
function tap(fn, x) {
  if(!isFunction(fn)) {
    throw new TypeError(
      'tap: Function required for first argument'
    )
  }

  return compose(constant(x), fn)(x)
}

module.exports = curry(tap)