AJAX ASP Example

AJAX is used to create more interactive applications.

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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 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 code:

Example

Start typing a name in the input field below:

Suggestions:

First name:

function showHint(str) {

  if (str.length == 0) {

    document.getElementById("txtHint").innerHTML = "";

    return;

  } else {

    const xmlhttp = new XMLHttpRequest();

    xmlhttp.onload = function() {

      document.getElementById("txtHint").innerHTML = this.responseText;

    }

  xmlhttp.open("GET", "gethint.asp?q=" + str);

  xmlhttp.send();

  }

}

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)="Anna" a(2)="Brittany" a(3)="Cinderella" a(4)="Diana" a(5)="Eva" a(6)="Fiona" a(7)="Gunda" a(8)="Hege" a(9)="Inga" a(10)="Johanna" a(11)="Kitty" a(12)="Linda" a(13)="Nina" a(14)="Ophelia" a(15)="Petunia" a(16)="Amanda" a(17)="Raquel" a(18)="Cindy" a(19)="Doris" a(20)="Eve" a(21)="Evita" a(22)="Sunniva" a(23)="Tove" a(24)="Unni" a(25)="Violet" a(26)="Liza" a(27)="Elizabeth" a(28)="Ellen" a(29)="Wenche" a(30)="Vicky" '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 %>