How to use JavaScript to define a class, javascript a class

How to use JavaScript to define a class, javascript a class

My original method is as follows:

function Dog(){  this.name = 'hachi';}Dog.prototype = {  makeNoise:function(){    alert('wangwangwang');  }};

Later, I saw another complicated and seemingly unnecessary statement:

function Dog(){  var privateVariable = 'secret';  var fn = function(){    //...  }  fn.prototype = {    makeNoise:function(){      alert('wangwangwang');    }  }  return fn;}

Here, the Dog function is actually a manufacturing function, which returns the real Dog class.
I feel that the advantage of doing so is better encapsulation.
For example, privateVariable is a private variable:

var d = new Dog;d.privateVariable //undefined

In addition, if you add the following sentence at the end of the first example:

Dog.prototype = {  //e...WTF??}

In this way, Dog is not a Dog ~

Later understanding:
The method for creating a new class directly overwrites the prototype object. In this way, prototype has no built-in attributes (arguments, call, apply, etc ).
The method for creating a class below seems better:

var Dog = function(name){  this.name = name;  var privateVariable = 'you cannot see me.';  this.getPrivate = function(){return privateVariable;};}

How does javascript define a class, attribute, and method? Write a program

// Define the Person class
Function Person (){
This. name = "Test"; // name attribute
This. age = 16; // age attribute
This. sex = "female"; // gender attribute

This. getName = function (){
// Obtain the name
Return this. name;
}
This. getAge = function (){
// Obtain the age
Return this. age;
}
This. getSex = function (){
// Obtain the Gender
Return this. sex;
}
}

Use

Var p = new Person ();
Alert (p. getName ());
Alert (p. getAge ());
Alert (p. getSex ());

How to define a boolean attribute in javascript?

Var a = true;
If (){
...
}

Note that the quotation marks are strings.