jQuery - Beginning JavaScript - page 503

alert("Please enter a user name to check!");
return;
}
You use $() to select the appropriate <input/> element and call the val() method. This retrieves the
value of the form control and assigns it to the userValue variable.
After you validate the user's input, you're ready to start issuing a GET request to the server. First, you
create an object to contain the information you want to send to the server:
var parms = {
username: userValue
};
You call this object parms and populate it with the username property. As you learned earlier in this
chapter, jQuery will add this property and its value to the query string.
Now, you can send the request using jQuery's getJSON() method:
$.getJSON("ch14_formvalidator.php", parms).done(handleResponse);
}
You add the handleResponse() function to the “done” queue, so that when the request successfully
completes, an alert box will display the search results.
The new checkEmail() function is very similar to checkUsername() . The two main differences, of
course, are the data you retrieve from the form and the data you send to the server:
function checkEmail(e) {
e.preventDefault();
var emailValue = $("#email").val();
if (!emailValue) {
alert("Please enter an email address to check!");
return;
}
var parms = {
email: emailValue
};
$.getJSON("ch14_formvalidator.php", parms).done(handleResponse);
}
The final function, handleResponse() , is mostly unchanged from the original version. Because
jQuery's getJSON() method automatically parses the response into a JavaScript object, the new
handleResponse() function simply uses the passed data as‐is:
function handleResponse(response) {
if (response.available) {
alert(response.searchTerm + " is available!");
} else {