AJAX Introduction by Bhanwar Gupta - HTML preview

Ajax – waiting for a response

• The readystate property of our
XMLHTTPRequest object can have the following values:

• 0 uninitialized
• 1 loading
• 2 loaded
• 3 interactive
• 4 completed

• .. But we only want the function to execute when the readystate has value 4

• {

• if (myRequest.readyState == 4 )
• {
• // code here
• } // else do nothing
• }

• {
• if (myRequest.readyState == 4 )
• {
• if ( myRequest.status == 200 ) // OK
• {
• // code goes here (success)
• }
• else
• {
• // code an error message here
• }
• } // else do nothing
• }

_ajax.status != 200 {
div=document.getElementById(‘status’) div.innerHTML = _ajax.responseText;

Save field onchange event:
_ajax = new XMLHTTPRequest(); _ajax.onreadystatechange = doResp; url = ‘./validate?field=’

Message
status=999
msg=Not a valid name

Get parameters…do some work Return something…
a text message
an XML document
an HTML snippet
a javascript method whatever you want…