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Exercises: funtional programming, RamdaJs lib,
Raw
index.html
<!DOCTYPE html>
<html>
<head>
<script src="http://cdnjs.cloudflare.com/ajax/libs/lodash.js/2.4.1/lodash.min.js"></script>
<meta charset="utf-8">
<title>JS Bin</title>
<script src="https://frontendmasters.com/assets/resources/functionaljs/pointfree.browser.js"></script>
<script src="https://frontendmasters.com/assets/resources/functionaljs/data.maybe.umd.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/ramda/0.8.0/ramda.min.js"></script>
</head>
<body>
<script id="jsbin-javascript">
var _ = R;
var get = _.curry(function(x, obj) { return obj[x]; });
/******************************************
C O M P O S I T I O N E X A M P L E
******************************************/
// Curried functions are easy to compose.
// Using _.map, _.size, and _.split we can
// make a function that returns the lengths
// of the words in a string.
var lengths = _.compose(
_.map(_.size), _.split(' ')
);
console.log(lengths('once upon a time'));
/*******************************************
Y O U R T U R N
********************************************/
var articles = [
{
title: 'Everything Sucks',
url: 'http://do.wn/sucks.html',
author: {
name: 'Debbie Downer',
email: 'debbie@do.wn'
}
},
{
title: 'If You Please',
url: 'http://www.geocities.com/milq',
author: {
name: 'Caspar Milquetoast',
email: 'hello@me.com'
}
}
];
// -- Challenge 1 -------------------------
// Return a list of the author names in
// articles using only get, _.compose, and
// _.map.
var names = _.map(
_.compose(get('name'), get('author'))
); // change this
assertEqualArrays(
['Debbie Downer', 'Caspar Milquetoast'],
names(articles)
);
// -- Challenge 2 -------------------------
// Make a boolean function that says whether
// a given person wrote any of the articles.
// Use the names function you wrote above
// with _.compose and _.contains.
var isAuthor = (name, articles) => _.compose(_.contains(name), names)(articles);
assertEqual(
false,
isAuthor('New Guy', articles)
);
assertEqual(
true,
isAuthor('Debbie Downer', articles)
);
// -- Challenge 3 -------------------------
// There is more to point-free programming
// than compose! Let's build ourselves
// another function that combines functions
// to let us write code without glue variables.
var fork = _.curry(function(lastly, f, g, x) {
return lastly(f(x), g(x));
});
// As you can see, the fork function is a
// pipeline like compose, except it duplicates
// its value, sends it to two functions, then
// sends the results to a combining function.
//
// Your challenge: implement a function to
// compute the average values in a list using
// only fork, _.divide, _.sum, and _.size.
var avg = fork(_.divide, _.sum, _.size);
assertEqual(3, avg([1,2,3,4,5]));
console.log("All tests pass.");
/******************************************
B A C K G R O U N D C O D E
*******************************************/
function assertEqualArrays(x,y) {
if(x.length !== y.length)
throw("expected "+x+" to equal "+y);
for(var i in x) {
if(x[i] !== y[i]) {
throw("expected "+x+" to equal "+y);
}
}
}
function assertEqual(x,y){
if(x !== y)
throw("expected "+x+" to equal "+y);
}
</script>
<script id="jsbin-source-html" type="text/html"><!DOCTYPE html>
<html>
<head>
<script src="http://cdnjs.cloudflare.com/ajax/libs/lodash.js/2.4.1/lodash.min.js"><\/script>
<meta charset="utf-8">
<title>JS Bin</title>
<script src="https://frontendmasters.com/assets/resources/functionaljs/pointfree.browser.js"><\/script>
<script src="https://frontendmasters.com/assets/resources/functionaljs/data.maybe.umd.js"><\/script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/ramda/0.8.0/ramda.min.js"><\/script>
</head>
<body>
</body>
</html>
</script>
<script id="jsbin-source-javascript" type="text/javascript">var _ = R;
var get = _.curry(function(x, obj) { return obj[x]; });
/******************************************
C O M P O S I T I O N E X A M P L E
******************************************/
// Curried functions are easy to compose.
// Using _.map, _.size, and _.split we can
// make a function that returns the lengths
// of the words in a string.
var lengths = _.compose(
_.map(_.size), _.split(' ')
);
console.log(lengths('once upon a time'));
/*******************************************
Y O U R T U R N
********************************************/
var articles = [
{
title: 'Everything Sucks',
url: 'http://do.wn/sucks.html',
author: {
name: 'Debbie Downer',
email: 'debbie@do.wn'
}
},
{
title: 'If You Please',
url: 'http://www.geocities.com/milq',
author: {
name: 'Caspar Milquetoast',
email: 'hello@me.com'
}
}
];
// -- Challenge 1 -------------------------
// Return a list of the author names in
// articles using only get, _.compose, and
// _.map.
var names = _.map(
_.compose(get('name'), get('author'))
); // change this
assertEqualArrays(
['Debbie Downer', 'Caspar Milquetoast'],
names(articles)
);
// -- Challenge 2 -------------------------
// Make a boolean function that says whether
// a given person wrote any of the articles.
// Use the names function you wrote above
// with _.compose and _.contains.
var isAuthor = (name, articles) => _.compose(_.contains(name), names)(articles);
assertEqual(
false,
isAuthor('New Guy', articles)
);
assertEqual(
true,
isAuthor('Debbie Downer', articles)
);
// -- Challenge 3 -------------------------
// There is more to point-free programming
// than compose! Let's build ourselves
// another function that combines functions
// to let us write code without glue variables.
var fork = _.curry(function(lastly, f, g, x) {
return lastly(f(x), g(x));
});
// As you can see, the fork function is a
// pipeline like compose, except it duplicates
// its value, sends it to two functions, then
// sends the results to a combining function.
//
// Your challenge: implement a function to
// compute the average values in a list using
// only fork, _.divide, _.sum, and _.size.
var avg = fork(_.divide, _.sum, _.size);
assertEqual(3, avg([1,2,3,4,5]));
console.log("All tests pass.");
/******************************************
B A C K G R O U N D C O D E
*******************************************/
function assertEqualArrays(x,y) {
if(x.length !== y.length)
throw("expected "+x+" to equal "+y);
for(var i in x) {
if(x[i] !== y[i]) {
throw("expected "+x+" to equal "+y);
}
}
}
function assertEqual(x,y){
if(x !== y)
throw("expected "+x+" to equal "+y);
}</script></body>
</html>
Raw
jsbin.kegujom.js
var _ = R;
var get = _.curry(function(x, obj) { return obj[x]; });
/******************************************
C O M P O S I T I O N E X A M P L E
******************************************/
// Curried functions are easy to compose.
// Using _.map, _.size, and _.split we can
// make a function that returns the lengths
// of the words in a string.
var lengths = _.compose(
_.map(_.size), _.split(' ')
);
console.log(lengths('once upon a time'));
/*******************************************
Y O U R T U R N
********************************************/
var articles = [
{
title: 'Everything Sucks',
url: 'http://do.wn/sucks.html',
author: {
name: 'Debbie Downer',
email: 'debbie@do.wn'
}
},
{
title: 'If You Please',
url: 'http://www.geocities.com/milq',
author: {
name: 'Caspar Milquetoast',
email: 'hello@me.com'
}
}
];
// -- Challenge 1 -------------------------
// Return a list of the author names in
// articles using only get, _.compose, and
// _.map.
var names = _.map(
_.compose(get('name'), get('author'))
); // change this
assertEqualArrays(
['Debbie Downer', 'Caspar Milquetoast'],
names(articles)
);
// -- Challenge 2 -------------------------
// Make a boolean function that says whether
// a given person wrote any of the articles.
// Use the names function you wrote above
// with _.compose and _.contains.
var isAuthor = (name, articles) => _.compose(_.contains(name), names)(articles);
assertEqual(
false,
isAuthor('New Guy', articles)
);
assertEqual(
true,
isAuthor('Debbie Downer', articles)
);
// -- Challenge 3 -------------------------
// There is more to point-free programming
// than compose! Let's build ourselves
// another function that combines functions
// to let us write code without glue variables.
var fork = _.curry(function(lastly, f, g, x) {
return lastly(f(x), g(x));
});
// As you can see, the fork function is a
// pipeline like compose, except it duplicates
// its value, sends it to two functions, then
// sends the results to a combining function.
//
// Your challenge: implement a function to
// compute the average values in a list using
// only fork, _.divide, _.sum, and _.size.
var avg = fork(_.divide, _.sum, _.size);
assertEqual(3, avg([1,2,3,4,5]));
console.log("All tests pass.");
/******************************************
B A C K G R O U N D C O D E
*******************************************/
function assertEqualArrays(x,y) {
if(x.length !== y.length)
throw("expected "+x+" to equal "+y);
for(var i in x) {
if(x[i] !== y[i]) {
throw("expected "+x+" to equal "+y);
}
}
}
function assertEqual(x,y){
if(x !== y)
throw("expected "+x+" to equal "+y);
}
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