Using Prototype on JS

Question

I am in need of a help in the use of Prototypes, I want to organize and maintain a cleaner code and can reuse my classes at other times... And in the research the use of Prototype seems to be something advantageous... (I may have got it wrong, correct me...)

First I’ll put my code down and then my doubts...

var Model = function(hello) {
    this.hello = hello; 

    //meu teste
    this._init();
}

Model.prototype = function(){
    var _init = function(){
        console.log("Init...");

        this.helloWorld();
    },

    _helloWorld = function(){
        alert(this.hello)
    };

    return {
        helloWorld : _helloWorld
    };
}();

1° Doubt: Inside my Builder how could I call my function "_init"? Since it’s private, I’d like you to take the first call inside the builder.. In my example above, I made the call via "this. _init()", but had the error:

Uncaught TypeError: this._init is not a function

2° Doubt: Within my "_init" function will I, and will I have calls from other methods, in this example: "_helloWorld", would the way I did work? Or what the right way?

Valeu Pessoal.

Answer 1

The point is that you didn’t export the function _init to the body of prototype, as it did with the function helloWorld; thus, it will exist only in the local scope of the function that defines the prototype, but not on the object itself. To solve, simply export the function:

var Model = function(hello) {
    this.hello = hello; 

    // Chamando o método "init"
    this.init();
}

Model.prototype = function(){
    var _init = function(){
        console.log("Init...");

        this.helloWorld();
    },

    _helloWorld = function(){
        console.log('Hello ' + this.hello)  // Alterei para console.log para facilitar a visualização
    };

    return {
        init: _init,  // Exportanto para o prototype a função _init
        helloWorld : _helloWorld
    };
}();

const m = new Model('world');

But ES6 has defined the class structure in Javascript and has a very good support already, except in the IE family. With her, you can do:

class Model {
  constructor(name) {
    this.name = name
  }
  
  hello() {
    console.log('Hello ' + this.name)
  }
}

const m = new Model('world')

m.hello()

You can read more about the classes in MDN: Classes in Javascript.

Related:

• There is a class in Javascript?
• How prototypes work in Javascript?
• What is the programming paradigm used by Javascript?
• What is a Javascript Prototype?
• Is there any way to extend an object in javascript?