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Selected library

Chartjs is a free and open source library widely used by the comunity, it supports several types of charts like the doughnut.

Usage

From the library docs

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#Shapes Using the new ES6 features related to prototyping, implement a small library to define geometric shapes (not visually) and allow basic calculations. ###Requirements

• The shapes to define are Circle, Square and Rectangle.
• All shapes must define a function to calculate the area and perimeter .
• Use a only positive coordinate system (implement validations while building the shapes or changing its properties).
• Implement a predicate function collidesWith to check if the shape collides with another shape of the same type.
• Given a list of shapes, print its properties and the area and perimeter properties.
• All functionalities should be properly tested.

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Callbacks

Are basically functions that are called when some result is ready or they can also be used to signal errors.

function aDividedByB(a, b, onResultFn, onErrorFn) {
  if (b != 0) {
    return onResultFn(a / b);
  }
  return onErrorFn("The divisor can't be zero!");
}

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Node Error first callback

The expected callback function

This kind of callback function have the error as the first parameter and the actual value as the second

function incrementAndLog(err, value) {
  if (err) {
    console.log("there's no value to increment");
    return;

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Call apply and bind

Call and Apply

The call and apply functions are similar, they expect a the contex (this) and the parameter to call the function, the only difference is that apply accepts the function parameters in an array.

const calculate = function(x, y) {
  return this.operation(x, y);
}

const multiply = {

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Async / Await

Async and await let us handle asynchronous code easily, it's somehow similar to generators, pausing the execution whenever the await is prefixed:

// To be able to wait for a call we need to mark a function as async
async function getTemperature () {
// We wait until the getWeather function returns the value
  const weather = await getWeather(....);
 

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Mixins

Mixins favors composition over inheritance by adding some custom behavior to an existing object

const fulfillable = {
  fullfill: (doneFunction) => done("OK")
};

const myObj = {
 quit: () => console.log("quit"),

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Coercion

Coercion is an implicit conversion of types:

// amount is a number
var amount = 32;

// since " years" is a string there is a implicit conversion of amount to string
var age = amount + " years";
console.log(age); // => 32 years

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Modern JavaScript

Template literals

Multiline strings

Default parameters

Classes

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export {}
// A monoid is a binary associative operation with an identity

// Laws
// 1 - Associativity: (x <> y) <> z = x <> (y <> z)
// 2 - Left identity: mempty <> x = x
// 3 - Right identity: x <> mempty = x

type Monoid<A = any> = {
  mempty: A,