w3schools    w3Schools
Search W3Schools :
   
HOME HTML CSS XML JAVASCRIPT ASP PHP SQL MORE...   References Examples Forum About
ADVERTISEMENTS

XML Certification
Download XML editor
Custom Programming
 
Table of contents
AJAX Basic
AJAX HOME
AJAX Intro
AJAX HTTP Request
AJAX Example
AJAX Browsers
AJAX XMLHttpRequest
AJAX Server
AJAX Server Script

AJAX Advanced
AJAX Suggest
AJAX Source
AJAX Database
AJAX XML File
AJAX ResponseXML

AJAX Examples
AJAX Examples

Selected Reading
Web Statistics
Web Glossary
Web Hosting
Web Quality

W3Schools Tutorials
W3Schools Forum

Helping W3Schools

 

AJAX Suggest Example

Previous Next

We have seen that AJAX can be used to create more interactive applications.


AJAX Suggest Example

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.


Type a Name in the Box Below

First Name:

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> 

As you can see 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 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.


Example Explained - The showHint() Function

The showHint() function is a very simple JavaScript function placed in the <head> section of the HTML page.

The function contains the following code:

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);
}

The function executes every time a character is entered in the input field.

If there is some input in the text field (str.length > 0) the 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 example above calls a function called GetXmlHttpObject().

The purpose of the function is to solve the problem of creating different XMLHTTP objects for different browsers. 

The function is listed below:

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;
}


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.


Previous Next


DreamTemplate



diploma   

Get Your Diploma!

W3Schools' Online Certification Program is the perfect solution for busy professionals who need to balance work, family, and career building.

The HTML Certificate is for developers who want to document their knowledge of HTML, XHTML, and CSS.

The JavaScript Certificate is for developers who want to document their knowledge of JavaScript and the HTML DOM.

The XML Certificate is for developers who want to document their knowledge of XML, XML DOM and XSLT.

The ASP Certificate is for developers who want to document their knowledge of ASP, SQL, and ADO.

The PHP Certificate is for developers who want to document their knowledge of PHP and SQL (MySQL).


 
WEB HOSTING
Web charting
Web based charting
for ASP.NET
$15 Domain Name
Registration
Save $20 / year!
Buy UK Domain Names
Register Domain Names
Cheap Domain Names
Cheap Web Hosting
Best Web Hosting
PHP MySQL Hosting
Top 10 Web Hosting
UK Reseller Hosting
Web Hosting
FREE Web Hosting
WEB BUILDING
Website Templates
Flash Templates
Website Builder
Internet Business Opportunity
Custom Programming
FREE Trial or Demo
Web Content Manager
Forms,Web Alerts,RSS
Download XML editor
FREE Flash Website
FREE Web Templates
EDUCATION
US Web Design Schools
HTML Certification
JavaScript Certification
XML Certification
PHP Certification
ASP Certification
Home HOME or Top of Page Validate   Validate   W3C-WAI level A conformance icon Printer Friendly  Printer Friendly

W3Schools is for training only. We do not warrant the correctness of its content. The risk from using it lies entirely with the user.
While using this site, you agree to have read and accepted our terms of use and privacy policy.
Copyright 1999-2009 by Refsnes Data. All Rights Reserved.