Section 2.16. Creating a request object | Head Rush Ajax (Head First)

2.16. Creating a request object

This step is all about making a request to the Break Neck server. For that, we need a request object that our JavaScript function can use. Luckily, though, you already wrote code that creates a request object back in Chapter 1, in the createRequest() function.

You should remember createRequest() from Chapter 1. Let's take a look at that JavaScript again, and make sure it's ready to use in the Break Neck app:

 Here's the top part of pizza.html, updated with the createRequest() function from Chapter 1.     <html>      <head>       <title>Break Neck Pizza Delivery</title>       <link rel="stylesheet" type="text/css" href="breakneck.css" />       <script language="javascript" type="text/javascript">       var request = null; Since requset isn't created inside a function, all your functions can use the request variable.       function createRequest() {         try {           request = new XMLHttpRequest();         } catch (trymicrosoft) {           try {             request = new ActiveXObject("Msxml2.XMLHTTP");Remember, we had to use different code for different browsers.           } catch (othermicrosoft) {             try {This was all pre-assembled JavaScript   in Chapter 1.We've pulled  this code out of its pre-assembled box... you're going to learn exactly what each line of this JavaScript does over the next few pages.               request = new ActiveXObject("Microsoft.XMLHTTP");             } catch (failed) {               request = null;             }           }        }        if (request == null) Our error checking here makes sure nothing went wrong.            alert("Error creating request object!");      }      function getCustomerInfo() {        var phone = document.getElementById("phone").value;        createRequest();        var url = "lookupCustomer.php?phone=" + escape(phone);        request.open("GET", url, true);        request.onreadystatechange = updatePage;        request.send(null);       }      </script>     </head>