Currying

New to Free Code Camp?

JS Concepts

JS Language Reference

Currying

It is the act of taking a function with more than one argument and converting it into an equivalent function that takes a single argument. This is based on returning partially applied functions.

Original

function add (verb, a, b) {
   return "The " + verb + " of " + a + ' and ' + b + ' is ' + (a + b)
 }

 add('sum', 5, '6')
   //=> 'The sum of 5 and 6 is 11'

Curried Version

function addCurried (verb) {
    return function (a) {
      return function (b) {
        return "The " + verb + " of " + a + ' and ' + b + ' is ' + (a + b)
      }
    }
  }

  addCurried('total')(6)(5)
   //=> 'The total of 6 and 5 is 11'

Currying by hand would be an incredible effort, but its close relationship with partial application means that if you have left partial application, you can derive currying. Or if you have currying, you can derive left partial application.

Here's a function that curries any function with two arguments:

  function curryTwo (fn) {
    return function (x) {
      return callFirst(fn, x)
    }
  }

  function add2 (a, b) { return a + b }

  curryTwo(add2)(5)(6)
   //=> 11

Learn to code and help nonprofits. Join our open source community in 15 seconds at http://freecodecamp.com

Follow our Medium blog
Follow Quincy on Quora
Follow us on Twitter
Like us on Facebook

And be sure to click the "Star" button in the upper right of this page.

FreeCodeCamp/FreeCodeCamp

Currying

Pages 616

Clone this wiki locally

Currying