JavaScript Encapsulation

The JavaScript Encapsulation is a process of binding the data (i.e. variables) with the functions acting on that data. It allows us to control the data and validate it. To achieve an encapsulation in JavaScript: -

Use var keyword to make data members private.
Use setter methods to set the data and getter methods to get that data.

The encapsulation allows us to handle an object using the following properties:

Read/Write - Here, we use setter methods to write the data and getter methods read that data.

Read Only - In this case, we use getter methods only.

Write Only - In this case, we use setter methods only.

JavaScript Encapsulation Example

Let's see a simple example of encapsulation that contains two data members with its setter and getter methods.

<script>
class Student
  {
    constructor()
    {
       var name;
       var marks;
    }
        getName()
        {
          return this.name;
        }
      setName(name)
      {
        this.name=name;
      }
      
      getMarks()
      {
        return this.marks;
      }
    setMarks(marks)
    {
      this.marks=marks;
    }

    }
    var stud=new Student();
     stud.setName("John");
     stud.setMarks(80);
     document.writeln(stud.getName()+" "+stud.getMarks());
</script>

Test it Now

Output:

John 80

JavaScript Encapsulation Example: Validate

In this example, we validate the marks of the student.

<script>
class Student
  {
    constructor()
    {
       var name;
       var marks;
    }
        getName()
        {
          return this.name;
        }
      setName(name)
      {
        this.name=name;
      }
      
      getMarks()
      {
        return this.marks;
      }
    setMarks(marks)
    {
        if(marks<0||marks>100)
        {
          alert("Invalid Marks");
        }
      else
        {
          this.marks=marks;
        }
    }
    }
    var stud=new Student();
     stud.setName("John");
     stud.setMarks(110);//alert() invokes
     document.writeln(stud.getName()+" "+stud.getMarks());
</script>

Test it Now

Output:

John undefined

JavaScript Encapsulation Example: Prototype-based approach

Here, we perform prototype-based encapsulation.

<script>
function Student(name,marks)
{
  var s_name=name;
  var s_marks=marks;
  Object.defineProperty(this,"name",{
    get:function()
    {
      return s_name;
    },
  set:function(s_name)
  {
    this.s_name=s_name;
  }
  
});
 
    Object.defineProperty(this,"marks",{
    get:function()
    {
      return s_marks;
    },
  set:function(s_marks)
  {
    this.s_marks=s_marks;
  }
  
});
  
}
  var stud=new Student("John",80);
  document.writeln(stud.name+" "+stud.marks);
</script>

Test it Now

Output: