(AJAX) Sending a Request to a Server

Let AJAX change this text.


Sending an XMLHttpRequest to a Server
The XMLHttpRequest object is used to exchange data with a server. To send a request to a server, we use the open and send methods of the XMLHttpRequest object: 
   xmlhttp.open( "GET", "AJAX_info.txt", true );
   xmlhttp.send( );
Method Description
open(method,url,async) Specifies the type of request, the URL, and if the request should be handled asynchronously or not.
  • method: the type of request: GET or POST
  • url: the location of the file on the server
  • async: true (asynchronous) or false (synchronous)
send(string) Sends the request off to the server.
string: Only used for POST requests


GET or POST?
GET is simpler and faster than POST, and can be used in most cases. However, always use POST requests when: 
<script type="text/javascript">
  function loadXMLDoc( ) {
    var xmlhttp;
    if ( window.XMLHttpRequest ) {
      // code for IE7+, Firefox, Chrome, Opera, Safari
      xmlhttp = new XMLHttpRequest( );
    }
    else {
      // code for IE6, IE5
      xmlhttp = new ActiveXObject( "Microsoft.XMLHTTP" );
    }
    xmlhttp.onreadystatechange = function( ) {
      if ( ( xmlhttp.readyState == 4 ) && 
           ( xmlhttp.status     == 200 ) ) {
        document.getElementById("myDiv").innerHTML =
          xmlhttp.responseText;
      }
    }
    xmlhttp.open( "GET", "AJAX_info.txt", true );
    xmlhttp.send( );
  }
</script>




      “What’s a couple?” I asked my mum.    
      She said, “Two or three.”    
      Which probably explains why her marriage collapsed.    
      — Josie Long