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Learning PHP, MySQL, and JavaScript by Robin Nixon

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JavaScript and HTML Text

JavaScript is a client-side scripting language that runs entirely inside the web browser. To call it up, you place it between opening <script> and closing </script> HTML tags. A typical HTML 4.01 “Hello World” document using JavaScript might look like Example 14-1.

Example 14-1. “Hello World” displayed using JavaScript

<html>
    <head><title>Hello World</title></head>
    <body>
        <script type="text/javascript">
            document.write("Hello World")
        </script>
        <noscript>
            Your browser doesn't support or has disabled JavaScript
        </noscript>
    </body>
</html>

Note

You may have seen web pages that use the HTML tag <script language="javascript">, but that usage has now been deprecated. This example uses the more recent and preferred <script type="text/javascript">.

Within the script tags is a single line of JavaScript code that uses its equivalent of the PHP echo or print commands, document.write. As you’d expect, it simply outputs the supplied string to the current document, where it is displayed.

You may also have noticed that, unlike PHP, there is no trailing semicolon (;). This is because a new line acts the same way as a semicolon in JavaScript. However, if you wish to have more than one statement on a single line, you do need to place a semicolon after each command except the last one. Of course, if you wish, you can add a semicolon to the end of every statement and your JavaScript will work fine.

The other thing to note in this example is the <noscript> and </noscript> pair of tags. ...

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