This document discusses JavaScript functions, arrays, objects, and classes. It shows examples of functions being first-class citizens that can be passed as arguments to other functions. Examples demonstrate using array methods like map, filter, and reduce to transform and extract data from arrays. Objects are manipulated using property accessors, and classes are defined with inheritance. Various syntax features are presented like let, const, arrow functions, destructuring, and modules.

1. Arcadio García Salvadores
Universidad Autónoma de Madrid
@arcadio_g_s
#MSPSpain

4. //Las funciones son de primera clase
var suma = function (a, b) {
return a + b;
}
//Y también son de orden superior
function aplicaTres(f,x) {
return f(3,x);
}
aplicaTres(suma,1); //4

5. var data = [{ user: 'pedro', msg: 'hola' }, { user: 'marta', msg:
'hola' }, { user: 'pedro', msg: 'adios' }, { user: 'admin',
msg: 'test' }];
var mensajes = data.map(function (x) { return x.msg; });
var mensajesFormat = data.map(function (x) {
return x.user + ' dice: ' + x.msg;
});

6. var data = [{user:'pedro',msg:'hola'}, {user:'marta',msg:'hola'},
{user:'pedro',msg:'adios'}, {user:'admin',msg:'test'}];
var mensajesPedro = data.filter( function (x) {
return x.user == 'pedro';
});

7. var data = [{user:'pedro',msg:'hola'}, {user:'marta',msg:'hola'},{user:'pedro',msg:'adios'},
{user:'admin',msg:'test'}];
var numeroMensajes = data.reduce( function (previousValue, currentValue, index, array) {
previousValue[currentValue.user]=(previousValue[currentValue.user] || 0) + 1;
return previousValue;
}, {});

8. function curry (fn, scope) {
var scope = scope || window;
var args = [];
for (var i=2, len = arguments.length; i < len; ++i) {
args.push(arguments[i]);
};
return function() {
fn.apply(scope, );
};
}
var add3=curry(sumar, this, 3);
add3(4); //7

11. var a = 0, b = 0;
function foo() {
var a = 1, b = 1;
if (true) {
var a = 2; //Redeclaracion
a = 2;
let b = 2; //b=2
}
//a=2, b=1
}
//a=0,b=0

12. var a=0;
let b=0;
const c=0;
const d=[1,2,3];
const e={x:3,y:2};
a=3;
b=3;
c=3; //ReferenceError
d.push(4);
d=[];//ReferenceError
e.z=4;

13. const d=[1,2,3];
const e={x:3,y:2};
e.z=3; //Se puede hacer
Object.seal(e); //No permite añadir mas valores
Object.freeze(e); //No permite modificar valores

14. var a = [1, 2, 3];
function sum(x, y, z) {
return x + y + z;
}
sum(...a); //6

15. function sum(...z) {
return z.reduce(function (previous, current) {
return previous + current;
});
}
sum(1, 2, 3, 4, 5); //15

16. function creaRobot (esAsesino){
...
}
creaRobot() ???

17. function creaRobot (esAsesino){
var asesino = esAsesino || false;
var asesino = (esAsesino !== undefined) ? esAsesino : false;
...
}
function creaRobot (esAsesino=false){
...
}

18. var a = [1,2,3];
var b = {x:1,y:2,z:3};
var [ax, ay, az] = a;
//ax==1, ay==2, az==3
var {bx, by, bz}=b;
//bx==1, by==2, bz==3
var {bx, by, bz=0}=b;

19. [1,2,3].map(function(x){ return x*x});
[1.2.3].map(x=>x*x);
NO altera this
var numero={
duplica: ()=> this*this;
}
numero.duplica(); //falla

20. var coordenadas = { x: 1, y: 2, z: 3 };
for (var i in coordenadas) {
console.log(i); //x,y,z
console.log(coordenadas[i]); //1,2,3
}
for(var i of coordenadas) {
console.log(i); //1,2,3
}

21. //matematicas.js
export function cuadrado(x){
return x*x
}
//main.js
import cuadrado from “matematicas.js”
import * as matematicas from “matematicas.js”
cuadrado(3);
matematicas.cuadrado(3);

22. class Vector{
constructor(x,y){
this.x=x;
thix.y=y;
}
modulo(){
return Math.sqrt(this.x*this.x+this.y*this.y);
}
}
var v1 = new Vector(1,1);

23. class NumeroComplejo extends Vector{
parteReal(){
return this.x;
}
parteImaginaria(){
return this.y;
}
}
var z1 = new NumeroComplejo(1,1);

24. let map = new Map();
map.set('foo', 123);
map.get('foo');
map.has(“foo”);
map.delete('foo');
map.has(“foo”);
map.forEach((value,key)=>console.log(value,key));

25. let set = new Set(); //o WeakSet
set.add('foo');
set.size();
set.has(“foo”);
set.delete('foo');
set.has(“foo”);
set.forEach((value,key)=>console.log(value,key));

26. var new
u32[2]=3;
u32[0]=“a”;
u32[20]=4;

29. https://github.com/getify/You-Dont-Know-JS
http://exploringjs.com
Youtube: @mpjm, @jsconf
dev.modern.ie, MDN
http://caniuse.com

30. https://github.com/uamnet/techtalks