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<p>From <b>http://www.w3schools.com</b> (Copyright Refsnes Data)</p>
<h1>AJAX Suggest Example</h1>
<a href="ajax_serverscript.asp"><img border="0" src="../images/btn_previous.gif" width="100" height="20" alt="Previous" /></a>
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<p class="intro">We have seen that AJAX can be used to create more interactive applications. </p>
<hr />
<h2>AJAX Suggest Example</h2>
<p>In the AJAX example below we will demonstrate how a web page can communicate
with a web server online as a user enters data into a standard HTML form. </p>
<hr />
<h2>Type a Name in the Box Below</h2>
<form action="">
First Name:
<input type="text" id="txt1"
onkeyup="showHint(this.value)" />
</form>
<p>Suggestions: <span id="txtHint"></span></p>
<hr />
<h2>Example Explained - The HTML Form</h2>
<p>The form above has the following HTML code:</p>
<table class="ex" width="100%" border="1" id="table1"><tr><td>
<pre><form>
First Name:
<input type="text" id="txt1"
onkeyup="showHint(this.value)">
</form></pre>
<pre><p>Suggestions: <span id="txtHint"></span></p> </pre>
</td></tr></table>
<p>
As you can see it is just a simple HTML form with an input
field called "txt1".</p>
<p>
An event attribute for the input field defines a function to be triggered by the
onkeyup event. </p>
<p>The paragraph below the form contains a span called "txtHint". The span is
used as a placeholder for data retrieved from the web server.</p>
<p>When the user inputs data, a function called "showHint()" is executed. The
execution of the function is triggered by the "onkeyup" event. In other words:
Each time the user moves his finger away from a keyboard key inside the input
field, the function showHint is called.</p>
<hr />
<h2>Example Explained - The showHint() Function</h2>
<p>The showHint() function is a very simple JavaScript function placed in the
<head> section of the HTML page.</p>
<p>The function contains the following code:</p>
<table class="ex" width="100%" border="1" id="table2"><tr><td>
<pre>function showHint(str)
{
if (str.length==0)
{
document.getElementById("txtHint").innerHTML="";
return;
}
xmlHttp=GetXmlHttpObject();
if (xmlHttp==null)
{
alert ("Your browser does not support AJAX!");
return;
}
var url="gethint.asp";
url=url+"?q="+str;
url=url+"&sid="+Math.random();
xmlHttp.onreadystatechange=stateChanged;
xmlHttp.open("GET",url,true);
xmlHttp.send(null);
}</pre>
</td></tr></table>
<p>The function executes every time a character is entered in the input field.</p>
<p>If there is some input in the text field (str.length > 0) the function
executes the following:</p>
<ul>
<li>Defines the url (filename) to send to the server</li>
<li>Adds a parameter (q) to the url with the content of the input field </li>
<li>Adds a random number to prevent the server from using a cached file</li>
<li>Creates an XMLHTTP object, and tells the object to execute a function
called stateChanged when
a change is triggered</li>
<li>Opens the XMLHTTP object with the given url.</li>
<li>Sends an HTTP request to the server</li>
</ul>
<p>If the input field is empty, the function simply clears the content of the txtHint
placeholder.</p>
<hr />
<h2>Example Explained - The GetXmlHttpObject() Function</h2>
<p>The example above calls a function called GetXmlHttpObject().</p>
<p>The purpose of the function is to solve the problem of creating different
XMLHTTP objects for different browsers. </p>
<p>The function is listed below:</p>
<table class="ex" width="100%" border="1" id="table4"><tr><td>
<pre>function GetXmlHttpObject()
{
var xmlHttp=null;
try
{
// Firefox, Opera 8.0+, Safari
xmlHttp=new XMLHttpRequest();
}
catch (e)
{
// Internet Explorer
try
{
xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");
}
catch (e)
{
xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
}
}
return xmlHttp;
}</pre>
</td></tr></table>
<br />
<hr />
<h2>Example Explained - The stateChanged() Function</h2>
<p>The stateChanged() function contains the following code:</p>
<table class="ex" width="100%" border="1" id="table3"><tr><td>
<pre>function stateChanged()
{
if (xmlHttp.readyState==4)
{
document.getElementById("txtHint").innerHTML=xmlHttp.responseText;
}
}</pre>
</td></tr></table>
<p>The stateChanged() function executes every time the state of the XMLHTTP
object changes.</p>
<p>When the state changes to 4 ("complete"), the content of the txtHint
placeholder is filled with the response text.</p>
<hr />
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<p>From <b>http://www.w3schools.com</b> (Copyright Refsnes Data)</p>
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