Datasheet

Chapter 1: AJAX Technologies

displays the login dialog box, and sets the display property of this DOM element’s style property to

none to hide the dialog box:

var credentials = document.getElementById(“credentials”);

credentials.style.display=”none”;

Next, readyStateChangeCallback invokes the getElementById method again, this time to return a

reference to the table DOM element that displays the server data, and sets the

display property of this

DOM element’s

style property to block to show this DOM element:

var employeeinfotable = document.getElementById(“employeeinfo”);

employeeinfotable.style.display=”block”;

Then, it invokes the responseText property on the XMLHttpRequest object to return a string that con-

tains the server data:

var response = request.responseText;

Keep in mind that the server data is in the following format:

Shahram|Khosravi|22223333|Some Department|

The next order of business is to deserialize an employee object from the server data. The following

excerpt from Listing 1-2 defines the

employee class:

window.employee = function window$employee(firstname, lastname,

employeeid, departmentname)

{

this.firstname = firstname;

this.lastname = lastname;

this.employeeid = employeeid;

this.departmentname = departmentname

}

As you can see in the following excerpt from Listing 1-2 , the readyStateChangeCallback function

invokes a JavaScript function named

deserialize :

var employee = deserialize();

This deserialize JavaScript function encapsulates the logic that deserializes an employee object from the

server data (described in more detail later). This logic is what is referred to as the Serializer in Figure 1-2 .

Next, the

readyStateChangeCallback function uses DHTML to update the relevant parts of the page

with employee information in the

employee object. First, it calls the getElementyById method on the

document object to return a reference to the <span> DOM element with the id HTML attribute of

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