luijar

var headLens = R.lensIndex(0); // point to first element in the array
R.view(headLens, people); //=> ana
var array2 = R.set(headLens, 'OLIVIA', firstnames);  //=> ["OLIVIA", "LUIS", "CARLOS", "NESTOR", "MARIA"]
R.over(headLens, R.toLower, array2); //=> ["olivia", "LUIS", "CARLOS", "NESTOR", "MARIA"]

luijar

// Remove the first element
var people = [
    ana, luis, carlos, nestor, maria
];

function head(arr) {
  return arr.shift();
}
head(people); // side effect (changed the content of the original array - people)
console.log(firstnames(people)); //-> ["LUIS", "CARLOS", "NESTOR", "MARIA"]

luijar

// Collection of person objects
var people = [  
    ana, luis, carlos, nestor, maria
];

var firstnames = 
    R.compose(
      R.map(R.view(firstnameLens)),     
      R.map(R.over(firstnameLens, R.toUpper)));
                           

luijar

var ana = new Person('Ana', 'Gonzalez');
var firstnameLens = R.lensProp('firstname');

// read firtstname
R.view(firstnameLens, ana); //-> 'Ana'           

// transform firstname to upper case
R.over(firstnameLens, R.toUpper, ana); //-> 'ANA'

// set firstname (creates a branch new object)

luijar

class Person {  
  constructor(firstname, lastname) {
      this._firstname = firstname;
      this._lastname = lastname;      
   }
   
   // returns a new copy of the object
   set firstname(f) {
      return new Person(f, this._lastname);
   }

luijar

function money(value, currency) {
        var _value = value;
        var _currency = currency;

        return {
            value: function () {
                return _value;
            },
            currency: function () {
                return _currency;

luijar

class Person {
   constructor(firstname, lastname) {
      this._firstname = firstname;
      this._lastname = lastname;      
   }

   set firstname(f) {
      this._firstname = f;
   }

luijar

/*
 * Functional Programming in JavaScript
 * Chapter 01
 * Magical -run- function in support of Listing 1.1
 * Author: Luis Atencio
 */
// -run- with two functions 
var run2 = function(f, g) {
    return function(x) {
        return f(g(x));