03-scope.txt

1. Al asignar una funcion a un variable se pierde el ambito

var x=10
var foo = {
    x:11,
    write:funcion(){console.log(this.x)}
}
foo.write() //11
var write = window.foo.write;
write() //10


window.x=10
window.foo = {
    x:11,
    write:function(){console.log(this.x)}
}
       //this
window.foo.write() //11
       //window
window.write = window.foo.write;  //pierdes el ambito
//window.write = window.foo.write.bind(window.foo);  //estableces el ambito
window.write = window.foo.write                   //pierdes el ambito
       //widow
window.write() //10

explorador->window
nodejs->Global

2. Al pasar una funcion como parametro a otra funcion perdemos ambito

class Foo{

  constructor(){
    //new Bar(this.writer) //perdida de ambito
    //new Bar(this.writer.bind(this)) //se establece
    new Bar(()=>this.writer())  //2 llamadas en el stack no se pierde por la funcion flecha
  }
  writer(){
    console.log(this)
  }
}

class Bar{
    constructor(writer){
        writer()    //undefined
        this.writer = writer;
        this.writer() //Bar
    }
}

//https://developer.mozilla.org/es/docs/Web/JavaScript/Reference/Functions/Arrow_functions

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/bind
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/call
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/apply
//call y apply

bar = {}
function foo(lastName,firstName){
    this.lastName =lastName
    this.firstName = firstName
}

foo.call(bar,"Pedro", "Hurtado")


bar = {}
function foo(lastName,firstName){
    this.lastName =lastName
    this.firstName = firstName
}

foo.apply(bar,["Pedro", "Hurtado"])