Why doesn't my httpRequest Javascript function return unless I add an
alert? Grrr.
I am writing my first AJAX-y function called add_tag. This is how it
is suppose to work:
1. define a username
2. create an httpRequest object
3. define what it is suppose to happen when it gets a response
4. open a connection to the server
5. send the request
When the response it is complete is simply echos the username. I know
the remote CGI script works because the following URL works correctly:
http://mylibrary.library.nd.edu/demos/tagging/?
cmd=add_tag&username=fkilgour
My Javascript is below, and it works IF I retain the "alert
( 'Grrr!' )" line. Once I take the alert out of the picture I get a
Javascript error "xmldoc has no properties". Here's my code:
function add_tag() {
// define username
var username = 'fkilgour';
// create an httpRequest
var httpRequest;
if ( window.XMLHttpRequest ) { httpRequest = new XMLHttpRequest(); }
else if ( window.ActiveXObject ) { httpRequest = new ActiveXObject
( "Microsoft.XMLHTTP" ); }
// give the httpRequest some characteristics and send it off
httpRequest.onreadystatechange = function() {
if ( httpRequest.readyState == 4 ) {
var xmldoc = httpRequest.responseXML;
var root_node = xmldoc.getElementsByTagName( 'root' ).item( 0 );
alert ( root_node.firstChild.data );
}
};
httpRequest.open( 'GET', './index.cgi?cmd=add_tag&username=' +
username, true );
httpRequest.send( '' );
alert ( 'Grrr!' );
}
What am I doing wrong? Why do I seem to need a pause at the end of my
add_tag function? I know the anonymous function -- function() -- is
getting executed because I can insert other httpRequest.readyState
checks into the function and they return. Grrr.
--
Eric Lease Morgan
University Libraries of Notre Dame
(574) 631-8604
