Example - AJAX Suggest
AJAX can be used to create more interactive applications.
AJAX Suggest example
The following AJAX example will demonstrate how a web page can communicate with a web server while a user enters data into an HTML form.
Type a name in the input field below:
Suggestions:
Example explained - The HTML form
The form above has the following HTML code:
<form>
First Name: <input type="text" id="txt1"
onkeyup="showHint(this.value)" />
</form>
<p>Suggestions: <span id="txtHint"></span></p> |
It is just a simple HTML form with an input field called "txt1".
An event attribute for the input field defines a function to be triggered by the onkeyup event.
The paragraph below the form contains a span called "txtHint". The span is used as a placeholder for data retrieved from the web server.
When a user inputs data, the function called "showHint()" is executed. The execution of the function is triggered by the "onkeyup" event. In other words:
Each time a user moves the finger away from a keyboard key inside the input field, the function showHint is called.
Example explained - The showHint() function
The showHint() function is a very simple JavaScript function placed in the
<head> section of the HTML page:
var xmlhttp
function showHint(str)
{
if (str.length==0)
{
document.getElementById("txtHint").innerHTML="";
return;
}
xmlhttp=GetXmlHttpObject();
if (xmlhttp==null)
{
alert ("Your browser does not support XMLHTTP!");
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);
} |
The function above executes every time a character is entered in the input field.
If there is input in the input field (str.length > 0), the showHint() function executes the following:
- Defines the URL (filename) to send to the server
- Adds a parameter (q) to the URL with the content of the input field
- Adds a random number to prevent the server from using a cached file
- Creates an XMLHTTP object, and tells the object to execute a function called stateChanged when a change is triggered
- Opens the XMLHTTP object with the given URL
- Sends an HTTP request to the server
If the input field is empty, the function simply clears the content of the txtHint placeholder.
Example explained - The GetXmlHttpObject() function
The showHint() function above calls a function named GetXmlHttpObject().
The purpose of the GetXmlHttpObject() function is to solve the problem of creating different XMLHTTP
objects for different browsers:
function GetXmlHttpObject()
{
if (window.XMLHttpRequest)
{
// code for IE7+, Firefox, Chrome, Opera, Safari
return new XMLHttpRequest();
}
if (window.ActiveXObject)
{
// code for IE6, IE5
return new ActiveXObject("Microsoft.XMLHTTP");
}
return null;
} |
Example explained - The stateChanged() function
The stateChanged() function contains the following code:
function stateChanged()
{
if (xmlhttp.readyState==4)
{
document.getElementById("txtHint").innerHTML=xmlhttp.responseText;
}
} |
The stateChanged() function executes every time the state of the XMLHTTP object changes.
When the state changes to 4 ("complete"), the content of the txtHint placeholder is filled with the response text.
Make your web applications look like a million bucks
|
|
Most web applications today use boring methods to present data to their viewers using grids or simple HTML tables. FusionCharts induces "life" into the web applications by converting monotonous data into lively charts, gauges & maps.
FusionCharts works with all technologies like ASP, ASP.NET, PHP, ColdFusion, Ruby on Rails, JSP, HTML pages etc.
and connects to any database to render animated & interactive charts. It takes less than 15 minutes and no expertise
whatsoever to build your first chart and just a glance of it to captivate your audience. This fact is endorsed by our
12,000 customers and 150,000 users which include a majority of the Fortune 500 companies.
And yeah, your applications could look like a million bucks by spending just $69.
So go ahead, download your
copy of FusionCharts and start "wow-ing" your customers now!
|
 |
W3Schools' Online Certification Program
The perfect solution for professionals who need to balance work, family, and career building.
More than 4000 certificates already issued!
|
The HTML Certificate documents your knowledge of HTML, XHTML, and CSS.
The JavaScript Certificate documents your knowledge of JavaScript and HTML DOM.
The XML Certificate documents your knowledge of XML, XML DOM and XSLT.
The ASP Certificate documents your knowledge of ASP, SQL, and ADO.
The PHP Certificate documents your knowledge of PHP and SQL (MySQL).
| 
