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AJAX ASP Example


AJAX is used to create more interactive applications.


AJAX ASP Example

The following example will demonstrate how a web page can communicate with a web server while a user type characters in an input field:

Example

Start typing a name in the input field below:

First name:

Suggestions:



Example Explained

In the example above, when a user types a character in the input field, a function called "showHint()" is executed.

The function is triggered by the onkeyup event.

Here is the HTML code:

Example

<html>
<head>
<script>
function showHint(str) {
    if (str.length == 0) {
        document.getElementById("txtHint").innerHTML = "";
        return;
    } else {
        var xmlhttp = new XMLHttpRequest();
        xmlhttp.onreadystatechange = function() {
            if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
                document.getElementById("txtHint").innerHTML = xmlhttp.responseText;
            }
        };
        xmlhttp.open("GET", "gethint.asp?q=" + str, true);
        xmlhttp.send();
    }
}
</script>
</head>
<body>

<p><b>Start typing a name in the input field below:</b></p>
<form>
First name: <input type="text" onkeyup="showHint(this.value)">
</form>
<p>Suggestions: <span id="txtHint"></span></p>
</body>
</html>

Code explanation:

First, check if the input field is empty (str.length == 0). If it is, clear the content of the txtHint placeholder and exit the function.

However, if the input field is not empty, do the following:

  • Create an XMLHttpRequest object
  • Create the function to be executed when the server response is ready
  • Send the request off to an ASP file (gethint.asp) on the server
  • Notice that q parameter is added gethint.asp?q="+str
  • The str variable holds the content of the input field

The ASP File - "gethint.asp"

The ASP file checks an array of names, and returns the corresponding name(s) to the browser:

<%
response.expires=-1
dim a(30)
'Fill up array with names
a(1)="Isabella"
a(2)="Ava"
a(3)="Cinderella"
a(4)="Emma"
a(5)="Eva"
a(6)="Sophia"
a(7)="Sophia"
'get the q parameter from URL
q=ucase(request.querystring("q"))

'lookup all hints from array if length of q>0
if len(q)>0 then
  hint=""
  for i=1 to 30
    if q=ucase(mid(a(i),1,len(q))) then
      if hint="" then
        hint=a(i)
      else
        hint=hint & " , " & a(i)
      end if
    end if
  next
end if

'Output "no suggestion" if no hint were found
'or output the correct values
if hint="" then
  response.write("no suggestion")
else
  response.write(hint)
end if
%>