Java script :

JavaScript is a most popular programming language. It is the language for websites and implemented as part of web browsers, so why it is called client side script.

Facts about Javascript :

* Javascript is a lightweight client side scripting language.
* JavaScript inserted into HTML pages, can be executed by all modern web browsers.
* JavaScript is an interpreted language. The scripts execute without preliminary compilation.
* Open and cross-platform.

You can use it to make your web pages interactive by :

* Responding to user actions and changes on the page.
* Manipulating the web page's contents and behavior.
* Communicating with the user directly

How/Where to place It :

Since javascript isn't HTML, you will need to let the browser know in advance when you enter javascript to an HTML page. This is done using the <script> tag. The browser will use the <script type="text/javascript"> and </script> to tell where javascript starts and ends. You can enter javascript in both the <head> and <body> sections of the document. In general however, it is advisable to keep as much as possible in the <head>section.

Example :
                    <html>
                        <head>
                           <title>My Javascript Page</title>
                        </head>
                        <body>
                            <script type="text/javascript">
                                document.write("Welcome to my world!!!");
                            </script>
                        </body>
                    </html>
Output :
Welcome to my world!!!

Embedding JS in HTML :

Inline JS

Internal JS

External JS

After editing Click here:
Output: