Javascript private, public properties and methods.

Javascript private properties and methods are declared with the keyword var. They can only be accessed within the function they were declared.
Javascript public properties and methods are declared with the keyword this. They can be accessed within or outside the function they were declared.

var Employee = function(id,name,department,salary,age)
{
	//public properties
	this.id=id;
	this.name=name;
	this.department=department;

	//private properties
	var salary=salary;
	var age=age;

	//public methods
	this.getSalary=function()
	{
		return salary;
	}
	this.getAge=function()
	{
		return age;
	}


	//public method
	this.iamPublicMethod = function()
	{
		console.log("I am a public method. I can be accessed from outside, and I can call any private mehtods or use any private properites within the parent function. Calling some private mehtod now...");
		iamPrivateMethod();
		anotherPrivateMethod();
	}


	//private methods
	var iamPrivateMethod = function()
	{
		console.log("I am a private method. If you see this text, then I must have been called within the parent function");
	}
	function anotherPrivateMethod()
	{
		console.log("I am also a private method. If you see this text, then I must have been called within the parent function");
	}
}

//Instantiating an employee object.
var e = new Employee(123,"Peng","Software Engineering", 99999,25);

//Directly access the the id, name and department because they are public properties.
console.log("ID: " + e.id);
console.log("Name: " + e.name);
console.log("Department: " + e.department);

//Calling public methods to get the value for salary and age becuase they are private properties.
console.log("Salary: " + e.getSalary());
console.log("Age: " + e.getAge());

//Calling a pulbic method
e.iamPublicMethod();

//Calling private mehtods and getting errors.
e.iamPrivateMethod();//will get error: Uncaught TypeError: Object [object Object] has no method 'iamPrivateMethod' since it is a private method
e.anotherPrivateMethod();//will get error: Uncaught TypeError: Object [object Object] has no method 'anotherPrivateMethod' since it is a private method

demo, Right click on the mouse, Inspect Element, Click console.