AJAX to validate data

[Bruce A. Julseth]

I'm new to AJAX and would appreciate some suggestions.

I want to use AJAX to search an existing database for information. If the
information exists, return true otherwise false. I am currently doing this
by submitting a php form and validating the data, then returning to then
reloading the client form with the true/false result. I have:

function validateStreet() {

var xmlhttp = getxmlhttp();
var serverPage = "validateStreet.php?street=";
var street = document.getElementById('Address').value;

serverPage += street;

xmlhttp.open("GET", serverPage);
xmlhttp.onreadystatechange = function() {
if(xmlhttp.readyState == 4 && xmlhttp.status == 200) {
result = xmlhttp.responseText;
alert(result);
}
}
xmlhttp.send(null);

return result;

}

In this code, "result" is correct when displayed by the alert, but result is
"undefined" when "returned."

How do I return the "xmlhttp.responseText" value?

Thank you.

Bruce

 

[Martin Honnen]

In this code, "result" is correct when displayed by the alert, but result is
"undefined" when "returned."

How do I return the "xmlhttp.responseText" value?

Well an 'A' in AJAX stands for 'asynchronous' as otherwise the HTTP
request would block the browser. So you need to process the response in
the onreadystatechange handler and use the result there, you can't
return a result from the function making the request.

 

[Bruce A. Julseth]

Well an 'A' in AJAX stands for 'asynchronous' as otherwise the HTTP
request would block the browser. So you need to process the response in
the onreadystatechange handler and use the result there, you can't return
a result from the function making the request.

Okay. I "Think" that explains why the alert works (that was within the
handler) but the return didn't. Right?

Thank you...

 

[Gregor Kofler]

Bruce A. Julseth meinte:

Okay. I "Think" that explains why the alert works (that was within the
handler) but the return didn't. Right?

Thank you...

Yes.

Gregor