Class en action

callback bis

Etudier le code précédent : https://jsfiddle.net/dupont/Lgre6msz/2/

On peut changer le code avec

class BD{


/**
* Finds items based on a query given as a JS object
*
* @param {function} function The function to filtre the query
* @param {function} callback   The callback to fire when the query has
* completed running
**/
    find ( fxFilter, callback) {

        callback(this.villes.filter( fxFilter))
     }
 

Callback

class BD{

    constructor(villes){
        this.villes = villes;
    }
   

/**
* Finds items based on a query given as a JS object
*
* @param {object} query The query to match against (i.e. {ville: 'paris'})
* @param {function} callback   The callback to fire when the query has
* completed running
**/
    find (query, callback) {

        callback(this.villes.filter(function(ville) {       
          for (let key in query) {
            if (query[key] !== ville[key]) {
              return false
            }
          }
          return true
        }))
      }
  }

// création d'une base
  bd = new BD([{ville:"vincennes",h:2},{ville:"paris",h:2},{ville:"roubais",h:1}]);

document.body.insertAdjacentHTML("beforeend",`<session>${JSON.stringify(bd.villes)}</session><p> 1`)


  bd.find({h:2},function(villes){
      for(let ville of villes){
        ville["h"]=30;
      }
  });
document.body.insertAdjacentHTML("beforeend",`<session>${JSON.stringify(bd.villes)}</session><p> 2`)

  bd.find({ville:"paris"},function(villes){
    for(let ville of villes){
       ville["capitale"]=true;
    }
});

document.body.insertAdjacentHTML("beforeend",`<session>${JSON.stringify(bd.villes)}</session><p>`)
 


https://jsfiddle.net/dupont/Lgre6msz/2/

findof versus filter

https://jsfiddle.net/dupont/s81evw7q/5/

Map en action

let p = '<h1>escapeForHTML<h1>';



let regex = /[<>&]/gi;



let r = new Map([
  ['>','&gt;'],

  ['&','&amp;'],

  ['<', '&lt;'],

]);


let f = c => r.get(c)


document.body.insertAdjacentHTML("afterbegin",p);

document.body.insertAdjacentHTML("afterbegin",p.replace(regex,f));

reduce

const posts = [
  {id: "moi", upVotes: 20},
  {id: "toi", upVotes: 89},
  {id: "lui", upVotes: 1},
  {id: "eux", upVotes: 123},];


let [premier,second] = posts.reduce((acc, cur) => [cur, ...acc].sort((a,b) => b.upVotes - a.upVotes).slice(0,2),[]);

console.log(`Au second tour sont présents : ${premier.id} et ${second.id}`);

Générateur

class Matrix {
  constructor(width, height, element = (x, y) => undefined) {
    this.width = width;
    this.height = height;
    this.content = [];

    for (let y = 0; y < height; y++) {
      for (let x = 0; x < width; x++) {
        this.content[y * width + x] = element(x, y);
      }
    }
  }

  get(x, y) {
    return this.content[y * this.width + x];
  }
  set(x, y, value) {
    this.content[y * this.width + x] = value;
  }

 *[Symbol.iterator]() {
          let i=0;
   
          while (i < this.height*this.width) {
              yield {
                x : i%this.width,
                y : Math.floor(i/this.width),
                value : this.content[i]
              }
              i++;
          }
  }
 
}


const width = 3;
let matrix = new Matrix(width, width, (x, y) => `[${x},${y}]= ${y * width + x}`);
for (let {value,x,y} of matrix) {
  console.log(x,y,value);
}

https://es6console.com/jppky2fw/

0 0 [0,0]= 0
1 0 [1,0]= 1
2 0 [2,0]= 2
0 1 [0,1]= 3
1 1 [1,1]= 4
2 1 [2,1]= 5
0 2 [0,2]= 6
1 2 [1,2]= 7
2 2 [2,2]= 8 

Autre exemple : lien