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Accepted
Eduardo Sebastian
Asked: 2020-09-26 02:39:52 +0800 CST 2020-09-26 02:39:52 +0800 CST

Why doesn't it work when assigning the prototype to it?

  • 772

Why can't I assign the prototype to c, like this so that it contains the methods of the class Array

c.prototype = Object.create(Array.prototype); // Aquí lo asigno


window.addEventListener('DOMContentLoaded',() => {
 var c = document.getElementsByClassName('clases'); 
  
 c.prototype = Object.create(Array.prototype);

 c.forEach(function(clase){
   
   console.log(clase.className);
 }); 
  
});
<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width">
  <title>JS Bin</title>
</head>
<body>
<a class="clases">Enlace 1</a>
<a class="clases">Enlace 2</a>
<a class="clases">Enlace 3</a>
<a class="clases">Enlace 4</a>
</body>
</html>

javascript

2 Answers

  1. Best Answer

    Because with

    Object.create(Array.prototype);

    what you do is create an object that has the same prototype as the class Array. therefore with

    c.prototype = Object.create(Array.prototype);

    you have an object cthat has an attribute prototypean object that has as its prototype the prototype of Array.

    Also think that when you create an instance of a class, this instance has the prototype assigned to <nombre_instancia>.__proto__it and not to <nombre_instancia>.prototype.

    You could actually do something like the following and it would be easier:

    var c= document.getElementsByTagName('div');

c.forEach=Array.prototype.forEach;

c.forEach(e => 
 console.log(e));
    <div/>
<div/>
<div/>

    • 3

  2. To consume the methods in the prototype, you have to initialize the object and the object chas already been initialized. You cannot modify the prototypeof an object at runtime unless you create a new instance of it:

    function carro(){
}

carro.prototype.correr = function(){
  console.log("corriendo");
}


var hyundai = new carro();
hyundai.correr();

hyundai.prototype = Object.create(Array.prototype);// ya el objeto hyundai fue creado, no puedes agregarle un prototipo en runtime
hyundai.push("2");

    If you want to "inherit" from some other object, you have to specify it in its definition:

        function carro(){
    }
    
    // 'heredamos' de array en la definicion del objeto
    carro.prototype = Object.create(Array.prototype);
    
    carro.prototype.correr = function(){
      console.log("corriendo");
    }

    
    var hyundai = new carro();
    hyundai.correr();
    hyundai.push("2");
    
    hyundai.forEach(function(value){ console.log(value) });

    • 3