How To Write Comments in JavaScript

JavaScript comments can be used to describe and explain JavaScript code, and to make the code it more readable and easy understandable.

Comments in JavaScript

Comment is nothing but it is a statement, Comments are not executed unlike the code on browser window.The javascript interpreter ignores the comments and continues execution till the end of file, when it encounters any comments.

Comment is also used to add information about the code, warnings or suggestions so that the end user or other developer can easily interpret the code.

There are 3-types of comments in JavaScript :

1. Single-Line Comment

2. Multi-Line Comment

3. ScriptDoc Comment

# Types of JavaScript Comments:

1.) Single-Line Comment : A single-line comment is represented by double forward slashes (//), It can be used before any statement.

 ➤ Example :

<script>
   // Write on browser
        document.write("Hello Javascript!");
   // Write text an <h2> Heading
 document.write("<h2> Hello Javascript! </h2>");  
 </script>

Output :

Hello Javascript!

Hello Javascript!

2.) Multi-Line Comment : Multiline comments are used for large text descriptions of code.

• A multi-line comment is represented by forward slash ( / )with asterisk (*) then asterisk with forward slash.

• Multiple-line comments start with forward slash and asterisk (/*), and end with the reverse asterisk and forward slash (*/).

Note : It is also used for single-line comment.

 ➤ Example :

<script>
   /*
      First line: Write Simple write
      Second line: Write text an <h2> Heading
   */
     document.write("Hello World!");
     document.write("<h2> Hello World! </h2>");  
 </script>

Output :

Hello World!

Hello World!

3.) ScriptDoc Comment / JavaScript Documentation Comment :

• ScriptDoc is JavaScript documentation technique, It is also known as JDC(JavaScript Documentation Comment).

• It's good habit to write remarks, arguments or notes etc. on JavaScript.

 ➤ Syntax :

    In JavaScript documentation style comment you can write following way :

<script>
   /** 
    * ScriptDoc technique to write comment
    * @TagName Description
    * @author   
    * @version 
    * ….
  **/ 
 </script>

Let's see the example of JavaScript Documentation Comment

 ➤ Example :

<script>
   /** 
    * Multiplication of two numbers 
    * @param {Number} a 
    * @param {Number} b 
    * @return {String} mult 
  **/ 
  function multiplication(a, b)
  { 
     mult = a * b;
     return "Output is : "+ mult.toString(); 
  }
  result = multiplication(7, 10);
  document.write(result);
</script>

Output :

Output is :70

ScriptDoc provides the many list of tags for documentation technique. There are few tags of ScriptDoc :

Tag	Description
@author Author-name [ email ]	Author of JavaScript file, functions, class.
@classDescription Description	Brief description of the Class.
@constructor	Specifies this function is a constructor.
@example Example-code	Describe a real example for how to use this function.
@id identifierName	Specifies ID for unique identification.
@inherits inherit_class	Specifies inherited class.
@memberOf Class	function, Property is member of specified class.
@method	Specifies the method name in class.
@exception { Exception }	Specifies exception type that throw this function.
@namespace namespaceName	Specifies the external library file.
@param { Type } ParameterName Parameter-Description	Specifies parameter of this function.
@private	Indicate that a class or function is private.
@projectDescription Description	Specifies on top of the page that describe the description of this file.
@property {Type}	Indicate that specified property are instance of the class.
@return {Type} Returns-Description	Specifies the return values of a function.
@type {Type}	Specify the data type of this property.
@version Version-Number	Specify the version number of file.