I want to have a javascript function such as this:
function isUsernameAvailable(username)
{
//Code to do an AJAX request and return true/false if
// the username given is available or not
}
How can this be accomplished using Jquery or Xajax?
The big win when using AJAX is that it is asynchronous. You're asking for a synchronous function call. This can be done, but it might lock up the browser while it is waiting for the server.
Using jquery:
function isUsernameAvailable(username) {
var available;
$.ajax({
url: "checkusername.php",
data: {name: username},
async: false, // this makes the ajax-call blocking
dataType: 'json',
success: function (response) {
available = response.available;
}
});
return available;
}
Your php-code should then check the database, and return
{available: true}
if the name is ok.
That said, you should probably do this asynchronously. Like so:
function checkUsernameAvailability(username) {
$.getJSON("checkusername.php", {name: username}, function (response) {
if (!response.available) {
alert("Sorry, but that username isn't available.");
}
});
}