[Javascript] IO Functor

IO functor doesn't like Maybe(), Either() functors. Instead of get a value, it takes a function.

API:

.toIO()  // conver a function to IO

IO() // The same a to toIO; but this is a just static method

runIO //IO is lazy, just like Observable, if you don't run it, it has no side effect

Examples:

/*

Cover to IO

*/

var email_io = IO(function(){ return $("#email").val() }

var getValue = function(sel){ return $(sel).val() }.toIO()

/*

Example runIO

*/

var email_io = IO(function(){ return $("#email").val() })

var msg_io = map(concat("welcome "), email_io)

runIO(msg_io)

//=> ”welcome [email protected]”

// Exercise 4

// ==========

// Get the text from the input and strip the spaces

console.log("--------Start exercise 4--------")

var getValue = function(x){ return document.querySelector(x).value }.toIO()

var stripSpaces = function(s){ return s.replace(/\s+/g, ''); }

var ex4 = compose(map(stripSpaces), getValue)

assertEqual("honkeytonk", runIO(ex4('#text')))

console.log("exercise 4...ok!")

// Exercise 5

// ==========

// Use getHref() / getProtocal() and runIO() to get the protocal of the page.

var getHref = function(){ return location.href; }.toIO();

var getProtocal = compose(_.head, _.split('/'))

var ex5 = compose(map(getProtocal), getHref)

console.log("--------Start exercise 5--------")

assertEqual('http:', runIO(ex5("http://www.google.fi")))

console.log("exercise 5...ok!")

// Exercise 6*

// ==========

// Write a function that returns the Maybe(email) of the User from getCache().

// Don't forget to JSON.parse once it's pulled from the cache

//so you can _.get() the email

// setup...

localStorage.user = JSON.stringify({email: "[email protected]"})

var log = function(x){

  console.log(x.toString());

  return x;

}

var getCache = function(x){ return Maybe(localStorage[x]); }.toIO();

var getEmail = compose(_.get('email'), JSON.parse);

var ex6 = compose(map(map(getEmail)), getCache); // one map for Maybe, one map for IO

assertDeepEqual(Maybe("[email protected]"), runIO(ex6('user')))

console.log("exercise 6...ok!")