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<h1>JavaScript Primer</h1>
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<p class="intro">An HTML file can contain text, HTML tags and scripts.
Scripts in an HTML file can be executed by the browser.</p>
<hr />
<h2>What is JavaScript?</h2>
<ul>
<li>JavaScript is a scripting language</li>
<li>A scripting language is a lightweight programming language</li>
<li>A JavaScript consists of lines of executable computer code</li>
<li>A JavaScript is usually embedded directly into HTML pages</li>
<li>JavaScript was designed to add interactivity to HTML pages</li>
<li>Everyone can use JavaScript without purchasing a
license</li>
</ul>
<p>JavaScript is used in millions of Web pages to improve the design, validate
forms, detect browsers, create cookies, and much more.</p>
<p>JavaScript is the most popular scripting language on the internet, and works
in all major browsers.</p>
<hr />
<h2>Client-Side Scripting</h2>
<p>JavaScript is about "programming" the behavior of the
browser. This is called client-side scripting or browser scripting.</p>
<p>Server-side scripting is about "programming" the behavior of the
server (see Web Scripting chapter).</p>
<hr />
<h2>What can a JavaScript Do?</h2>
<ul>
<li><b>JavaScript gives HTML designers a programming tool - </b>HTML authors
are normally not programmers, but JavaScript is a scripting language with a
very simple syntax! Almost anyone can put small "snippets" of code into their
HTML pages</li>
<li><b>JavaScript can put dynamic text into an HTML page - </b>A JavaScript statement like this: document.write("<h1>" + name +
"</h1>") can write a variable text into an HTML page</li>
<li><b>JavaScript can react to events - </b>A JavaScript can be set to execute
when something happens, like when a page has finished loading or when a user
clicks on an HTML element</li>
<li><b>JavaScript can read and write HTML elements - </b>A JavaScript can read
and change the content of an HTML element</li>
<li><b>JavaScript can be used to validate data - </b>A JavaScript can be used
to validate form data before it is submitted to a server. This saves the
server from extra processing</li>
<li><b>JavaScript can be used to detect the visitor's browser</b> - A
JavaScript can be used to detect the visitor's browser, and - depending on
the browser - load another page specifically designed for that browser</li>
<li><b>JavaScript can be used to create cookies</b> - A JavaScript can be
used to store and retrieve information on the visitor's computer</li>
</ul>
<hr />
<h2>How to Put a JavaScript Into an HTML Page</h2>
<table width="100%" border="1" class="ex" cellspacing="0" id="table1">
<tr><td>
<pre><html>
<body>
<span class="blue"><script type="text/javascript"></span>
<span class="red">document.write("Hello World!")
</span><span class="blue"></script>
</span></body>
</html></pre>
</td></tr>
</table>
<p>The code above will produce this output on an HTML page:</p>
<table width="100%" border="1" class="ex" cellspacing="0" id="table2"><tr><td>
Hello World!
</td></tr></table>
<h3>Example Explained</h3>
<p>To insert a JavaScript into an HTML page, we use the <script> tag. The type
attribute defines the scripting language.</p>
<p>So, the <script type="text/javascript"> tells where the
JavaScript starts:</p>
<table width="100%" border="1" class="ex" cellspacing="0" id="table3"><tr><td>
<pre><span class="blue"><script type="text/javascript"></span></pre>
</td></tr></table>
<p>The JavaScript command for writing some output to
a page is <b>document.write</b>:</p>
<table width="100%" border="1" class="ex" cellspacing="0" id="table4"><tr><td>
<pre><span class="red">document.write("Hello World!")</span></pre>
</td></tr></table>
<p>Then, the script ends:</p>
<table width="100%" border="1" class="ex" cellspacing="0" id="table5"><tr><td>
<pre><span class="blue"></script></span></pre>
</td></tr></table>
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<hr />
<h2>Try-It-Yourself Examples</h2>
<p><a target="_blank" href="../js/tryit.asp@filename=tryjs_text">Write text</a><br />
How to write text on a page.</p>
<p><a target="_blank" href="../js/tryit.asp@filename=tryjs_formattext">Write text with formatting</a><br />
How to format the text on your page with HTML tags.</p>
<hr />
<h2>JavaScript Tutorial</h2>
<p><a href="../js/default.asp">Study our Complete JavaScript tutorial</a></p>
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