Step by Step to AJAX

This short list of methods is shared by all supported browsers. In this tutorial we shall look at some of the highlighted methods.

abort()

current request is stopped

getAllResponseHeaders()

returns a string containing information of headers

getResponseHeader ("headerlabel")

returns a string containing information about a single header

open("method", "URL"[,asyncFlag[,"userName"[,"password"]]])

assigns various request attributes

send(content)

Transmits the data with information that may be posted, if needed

setRequestHeader ("label", "value")

assigns label, value pair for the header

While open() and send() are most often used, the others are also useful in some cases. The open() method begins the interaction and takes two mandatory arguments; the "method" used to open, which is either GET or POST, and the URL to which the request is made.

The GET and POST methods are similar to those used in ASP, as some of you might recognize. The GET is indicated for retrieving read only data while POST is for sending data to the server.

The URL could be complete, or a relative URL.

The third parameter which is optional (default value TRUE being asynchronous) sets the interaction to be synchronous (FALSE) or asynchronous (TRUE). If you choose the synchronous route, the script waits for the response to arrive before acting. The useful mode is to set the interaction to be asynchronous and use the  onreadystatechange event (to be discussed) to get at the response.

The following read only properties are browser agnostic (all supported browsers understand them).

onreadystatechange

Event handler which fires every time the state changes

readState

Integer representing the status of the object
0 = uninitialized
1 = loading
2 = loaded
3 = interactive
4 = complete

responseText

Data returned in string format

responseXML

Data returned in DOM Compatible format

status

Numeric code returned by server indicating status
404: Not found
200: OK

statusText

Message string that came with the status