JAVASCRIPT

why use currying

const createURL = baseURL => {
  const protocol = "https";

  // we now return a function, that accepts a 'path' as an argument
  return path => {
    return `${protocol}://${baseURL}/${path}`;
  };
};

// we create a new functions with the baseURL value in it's closure scope
const createSiteURL = createURL("mysite.com");
const createCareersURL = createURL("mysite-careers.com");

// create URLs for our main site
const homeURL = createSiteURL("");
const loginURL = createSiteURL("login");
const productsURL = createSiteURL("products");
const contactURL = createSiteURL("contact-us");

// create URLs for our career site
const careersHomeURL = createCareersURL("");
const careersLoginURL = createCareersURL("login");

what is currying

a technique that applies a function 
to its arguments one at a time, with 
each application returning a new function 
that accepts the next argument.

Understanding Currying

/**
 * The underlying base function is "add" which takes 3 arguments and return their sum.
 */
const add = (a, b, c) => a + b + c;

/**
 * We need such a function which will transform the base function such that
 * it can also process its argument one by one.
 */
const curry = (baseFunc) => {
  // TODO: Do something with it.
};

const add3 = curry(add);