Comments and Objects in JavaScript: Day 3

Introduction

This article explains some basic concepts of JavaScript used in Web Applications, like comments, objects, etc.

Before reading this article, I highly recommend reading the previous parts,

• Introduction to JavaScript: Day 1
• Programming Basics in JavaScript: Day 2

Comments in JavaScript

In JavaScript, comments are used for skipping that statement from execution; using comments, you make code more readable and understandable for anyone. Code functionality is clearer using comments. The following comments are used in JavaScript:

1. Single Line Comment
2. Multi-line comment

Single Line Comment in JavaScript

When you want to comment out a single statement, then a single-line comment is used; it starts with "//". JavaScript ignores this line. Using this, you can comment out an entire line.

The following example uses a single-line comment to explain the code,

<!DOCTYPE html>    
<html>    
<title>JavaScript Comments</title>    
<head></head>    
<body>    
<script language="javascript">    
    //Single line comment    
    //Addition of two numbers    
    var a = 25;    
    var b = 75;    
    var c = a + b; //addition of a and b is store in c variable    
    document.write("Addition of " + a + " and " + b + " is " + c);    
</script>    
</body>    
</html>   

Output

Addition of 25 and 75 is 100

Multi-line Comment in JavaScript

A multi-line comment is used with a group or code block that you want to comment out. A multi-line comment starts with /* and ends with */. JavaScript skips the code block between this.

In the following example, a group of statements is commented out using multi-line comments.

<!DOCTYPE html>    
<html>    
<title>JavaScript Comments</title>    
<head></head>    
<body>    
<script language="javascript">    
    /*  
    var a = 25;  
    var b = 75;  
    var c = a + b; //addition of a and b is store in c variable  
    document.write("Addition of " + a + " and " + b + " is " + c);  
    */    
    function Print() {    
        document.write("Example of Multi-line Comments in JavaScript");    
    }    
    Print();    
</script>    
</body>    
</html>   

Output

Example of Multi-line Comments in JavaScript

Objects in JavaScript

An object is a thing, just like things in the real world. Objects are a way to organize variables. In the web browser, objects include the browser window, forms and buttons, and so on. (For example, cars, books, dogs, and money.)

Properties and Methods in JavaScript

Every object has its properties and methods. Properties define the characteristics of an object. (For example, color, name, length.) Methods that can be done on objects.

(For example, alert, confirm, and open.)

The following is the syntax of properties:

objectName.propName or objectName[“property”]

The following is the syntax of methods,

methodName : function () { Statements; }   

Example

The following demo example explains the concept of objects, properties, and methods. In this example, an object is created named "employee". It has the property's name and city. Creating the method for this object employee and call.

<!DOCTYPE html>    
<html>    
<title>JavaScript Objects</title>    
<head></head>    
<body>    
<script language="javascript">    
    var employee = new Object(); //Creating an object    
    
    //Assigning properties to an object 'employee'    
    employee.name = "Jeetendra";    
    employee.city = "Pune";    
    
    //Assigning method to an object 'employee'    
    employee.info = function () {    
        document.write("Name : " + this.name + " City : " + this.city);    
    }    
    
    //calling the method    
    employee.info();    
</script>    
</body>    
</html>