/* * A simple abstraction class for doing AJAX * * $author = Paul Washburn * $date = 26 January 2008 * * (C) 2008 Paul Washburn */ /* * Purpose : Instantiates a XHR object for standards compliant browsers (first try) * or Internet Explorer (second and third try). This function should really * only be used internally. * * Returns : XMLHttpRequest object (or its Microsoft variants) * * Errors : Alerts the user, and returns NULL, if a XHR object cannot be instantiated */ function ajax_createXMLHttpRequestObject() { var xhr; try { xhr = new XMLHttpRequest(); } catch(e) { try { xhr = new ActiveXObject("Msxml2.XMLHTTP"); } catch (e2) { try { xhr = new ActiveXObject("Microsoft.XMLHTTP"); } catch (e) { alert('Your browser does not support AJAX. This application will not function properly'); return null; } } } return xhr; } /* * Purpose : This is the scripts XHR that it executes on. It is instantiated when * the page is loaded. It must also be used in user-defined callbacks * * SEE THE END OF THIS DOCUMENT FOR EXAMPLE USAGE !!! */ var ajax_xhr = ajax_createXMLHttpRequestObject(); /* * Purpose : Allows the user to specify a script, get parameters, and a callback function * that will use the XHR object resident in this script. * * Parameters : script = The name of the script that the XHR object will submit to * param_num = The number of parameters contained in the parameter array * params = Get parameters to send to $script * callback = The function to be executed when the XHR changes state. If * this is null, it defaults to ajax_defaultResponse * * Returns: VOID * * Exceptions : No externally relevant exception handling is present * * SEE THE END OF THIS DOCUMENT FOR EXAMPLE USAGE !!! */ function ajax_sendGetRequest(script,params,callback) { var build_url = script+'?'; for(i = 0; i < params.length; i++){ if(i > 0){ build_url+='&'; } build_url+=(params[i]); } ajax_xhr.open('get', build_url); if(callback == null){ ajax_xhr.onreadystatechange = ajax_defaultResponse; } else { ajax_xhr.onreadystatechange = callback; } ajax_xhr.send(null); } /* * Purpose : The default callback function. Creates an alert with the * responseText of the XHR object. This is mostly for debugging * purposes and to notify developers that they forgot to define * a valid callback * * Returns : VOID * * Errors : Entering in this function is an error of sorts. The alert box * notifies the user that this has occured. */ function ajax_defaultResponse() { if(ajax_xhr.readyState == 4 && ajax_xhr.status == 200){ if(ajax_xhr.responseText) { alert(ajax_xhr.responseText); } } } /* * Purpose : Returns the state and status of the XHR object * * Returns : TRUE if the object is both ready and has a normal status * FALSE otherwise * * Errors : N/A */ function ajax_getXML(){ if(ajax_xhr.readyState == 4 && ajax_xhr.status == 200){ return ajax_xhr.responseXML; } else { return false; } } /* ***************** * Example Usage * ***************** ******************************* * XML Schema for this example * ******************************* TEXT TEXT ... TEXT */