JavaScript How To

From http://www.w3schools.com (Copyright Refsnes Data)

# JavaScript How To

The HTML <script> tag is used to insert a JavaScript into an HTML page.

## Examples

Write text with Javascript
The example demonstrates how to use JavaSript to write text on a web page.

Write HTML with Javascript
The example demonstrates how to use JavaScript to write HTML tags on a web page.

## How to Put a JavaScript Into an HTML Page

    <html>
    <body>
    <script type="text/javascript">
    document.write("Hello World!");
    </script>
    </body>
    </html>

The code above will produce this output on an HTML page:

Hello World!

### Example Explained

To insert a JavaScript into an HTML page, we use the <script> tag. Inside the <script> tag we use the type attribute to define the scripting language.

So, the <script type="text/javascript"> and </script> tells where the JavaScript starts and ends:

    <html>
    <body>
    <script type="text/javascript">
    ...
    </script>
    </body>
    </html>

The word document.write is a standard JavaScript command for writing output to a page.

By entering the document.write command between the <script> and </script> tags, the browser will recognize it as a JavaScript command and execute the code line. In this case the browser will write Hello World! to the page:

    <html>
    <body>
    <script type="text/javascript">
    document.write("Hello World!");
    </script>
    </body>
    </html>

Try it yourself.

Note: If we had not entered the <script> tag, the browser would have treated the document.write("Hello World!") command as pure text, and just write the entire line on the page.

Try it yourself.

## HTML Comments to Handle Simple Browsers

Browsers that do not support JavaScript will display JavaScript as page content.

To prevent them from doing this, and as a part of the JavaScript standard, the HTML comment tag can be used to "hide" the JavaScript. Just add an HTML comment tag <!-- before the first JavaScript statement, and a --> (end of comment) after the last JavaScript statement.

    <html>
    <body>
    <script type="text/javascript">
    <!--
    document.write("Hello World!");
    //-->
    </script>
    </body>
    </html>

The two forward slashes at the end of comment line (//) is the JavaScript comment symbol. This prevents JavaScript from executing the --> tag.

From http://www.w3schools.com (Copyright Refsnes Data)