AJAX Suggest Example
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
Example Explained - The HTML Form
The form above has the following HTML code:
<input type="text" id="txt1"
<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
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
<head> section of the HTML page.
The function contains the following code:
alert ("Your browser does not support AJAX!");
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
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:
// Firefox, Opera 8.0+, Safari
// Internet Explorer
Example Explained - The stateChanged() Function
The stateChanged() function contains the following code:
The stateChanged() function executes every time the state of the XMLHTTP
When the state changes to 4 ("complete"), the content of the txtHint
placeholder is filled with the response text.
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