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VOOZH | about |
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Monads are all about making the composition of functions within code as simple as possible.They are commonly used when constructing enterprise-level applications that require the utmost accuracy. Monads can make code more manageable, resulting in complex callbacks, nested conditional branches, and so on. In essence, monads are all about making the composition of functions within code as simple as possible. Monads can be broken down into three types of function composition:
const composeM = chainMethod => (...ms) => (
ms.reduce((f, g) => x => g(x)[chainMethod](f))
);
const composePromises = composeM('then');
const label = 'API call composition';
// a => Promise(b)
const getUserById = id => id === 3 ?
Promise.resolve({ name: 'Kurt', role: 'Author' }) : undefined;
// b => Promise(c)
const hasPermission = ({ role }) => (
Promise.resolve(role === 'Author')
);
// Compose the functions (this works!)
const authUser = composePromises(hasPermission, getUserById);
authUser(3).then(trace(label)); // true
A declarative approach is often used when a developer prioritizes concise, expressive code.Declarative programming in JavaScript focuses on the overall goals of the code and not how these goals are achieved. This makes code much more simple and readable — therefore, making it easier to maintain. A declarative approach is often used when a developer prioritizes concise, expressive code to deliver projects quickly. Let’s compare a declarative approach to an imperative one: Imperative:
function evenSum(numbers) {
let result = 0;
for (let i = 0; i < numbers.length; i++) {
let number = numbers[i]
if (number % 2 === 0) {
result += number;
}
}
return result;
}
const evenSum = numbers => numbers .filter(i => i % 2 === 0) .reduce((a, b) => a + b)
Server-side caching could be used to automate the scaling of resources based on usage metrics.Caching is nothing new and may not be considered particularly cutting edge, but as both client-side and server-side web applications can use caching, it is a powerful tool for boosting performance. In particular, server-side caching can improve Node.js performance by speeding up data retrieval. Let’s take a look at a simple example of the memory-cache technique in use:
const cache = require('memory-cache');
function getDataFromCache(key) {
const cachedData = cache.get(key);
if (cachedData) {
return cachedData;
}
// If data is not in cache, fetch it from the source
const data = fetchDataFromSource();
// Store data in cache for future use
cache.put(key, data, 60000); // Cache for 60 seconds
return data;
}
This technique results in less debugging and fewer unexpected outcomes.Data that cannot be changed is important because it helps to enable consistency through the code base and helps with state management. Instead of changing a value, a new one is created, making things more predictable and thus reducing errors — like those that occur when a data structure unexpectedly changes. This results in less debugging and fewer unexpected outcomes. An example of immutability being used for name values:
// Import stylesheets
import './style.css';
// Write JavaScript code!
const appDiv = document.getElementById('app');
appDiv.innerHTML = `<h1>Open the console to see results</h1>`;
class Person {
//_name = "Nee";
//_name = ["Nee", "Ra"];
_name = { first: "Nee", middle: "L" };
get name() {
return this._name;
}
set name(value) {
console.log('In setter', value);
this._name = value;
}
}
let p = new Person();
//p.name = "Ra"; // Setter executes
//p.name.push("Lee"); // Setter doesn't execute
//p.name = [...p.name, "Lee"]; // Setter executes
//p.name.middle = "Lee"; // Setter doesn't execute
p.name = { ...p.name, middle: "Lee" }; // Setter executes
Pattern matching is much more effective than the standard switch statement.When it comes to testing a value against any given pattern, pattern matching is much more effective than the standard switch statement and provides much more control, allowing developers to write more complicated expressions. Here is an example of the factorial function being implemented with the match module, using the JUnify library:
match = function () {
var unify = unification.unify;
function match_aux(patterns, value) {
var i, result;
for (i = 0; i < patterns.length; i += 1) {
result = unify(patterns[i][0], value);
if (result) {
return patterns[i][1](result);
}
}
return undefined;
}
return function(patterns, value) {
return match_aux(patterns, value);
};
}();
var fact = function (n) {
return match([
[0, function() { return 1; }],
[$('n'), function(result) {
return result.n * fact(result.n - 1);
}]
], n);
};
