Functional Programming in Javascript

About

Code - Functional programming (FP) - Collection Operations in javascript.

Example

To get the cookies

console.log("Functional Programming: The cookies that we see with Javascript");

document.cookie
    .split(";")
    .map(cookie => cookie.split("="))
    .forEach(cookie=>console.log(cookie));

List

Collector

All function returns an array.

A few returns an element such as:

• find: returns the value of the first element in the provided array that satisfies the provided testing function.
• findIndex() method returns the index of the first element in the array that satisfies the provided testing function.

map

Javascript - Map function (Functional programming)

Map example 1

data = [
  { name: 'Nicolas', firstname: 'Gerard', surname: 'nico' },
  { name: 'Rixt', firstname: 'Van Der Veen', surname: 'konigin' }
]

console.log("Name");
names = data.map( function (d) { return d.name } )
console.log(names);

console.log("FirstName");
firstnames = data.map( function (d) { return d.firstname } )
console.log(firstnames);

console.log("Surname");
surnames = data.map( function (d) { return d.surname } )
console.log(surnames);

Map example 2 - select and process

var myList = [].slice.call(document.querySelectorAll('selector'))
myList.map(function (element) {
  // ....
});

Filter

filter functional programming function.

Example a split on a string that does contains a separator without value create an empty string element. We filter it below.

let s = "aStringWithoutSeparator.";

console.log("With filtering");
console.log( s.split ('.').filter(el => {return el.length != 0}));

console.log("Without filtering");
console.log(s.split ('.'))

Terminal

terminal function are all array function that does not produce an array such as:

• Javascript - foreach instruction
• join