//?AjaxRequest?object?constructor function?AjaxRequest()?{ ??//?Try?the?XMLHttpRequest?object?first ??if?(window.XMLHttpRequest)?{ ????try?{ ??????this.request?=?new?XMLHttpRequest(); ????}?catch(e)?{ ??????this.request?=?null; ????} ??//?Now?try?the?ActiveX?(IE)?version ??}?else?if?(window.ActiveXObject)?{ ????try?{ ??????this.request?=?new?ActiveXObject("Msxml2.XMLHTTP"); ????//?Try?the?older?ActiveX?object?for?older?versions?of?IE ????}?catch(e)?{ ??????try?{ ????????this.request?=?new?ActiveXObject("Microsoft.XMLHTTP"); ??????}?catch(e)?{ ????????this.request?=?null; ??????} ????} ??} ??//?If?the?request?creation?failed,?notify?the?user ??if?(this.request?==?null) ????alert("Ajax?error?creating?the?request.\n"?+?"Details:?"?+?e); } //?Send?an?Ajax?request?to?the?server AjaxRequest.prototype.send?=?function(type,?url,?handler,?postDataType,?postData)?{ ??if?(this.request?!=?null)?{ ????//?Kill?the?previous?request ????this.request.abort(); ????//?Tack?on?a?dummy?parameter?to?override?browser?caching ????url?+=?"?dummy="?+?new?Date().getTime(); ????try?{ ??????this.request.onreadystatechange?=?handler; ??????this.request.open(type,?url,?true);?//?always?asynchronous?(true) ??????if?(type.toLowerCase()?==?"get")?{ ????????//?Send?a?GET?request;?no?data?involved ????????this.request.send(null); ??????}?else?{ ????????//?Send?a?POST?request;?the?last?argument?is?data ????????this.request.setRequestHeader("Content-Type",?postDataType); ????????this.request.send(postData); ??????} ????}?catch(e)?{ ??????alert("Ajax?error?communicating?with?the?server.\n"?+?"Details:?"?+?e); ????} ??} } AjaxRequest.prototype.getReadyState?=?function()?{ ??return?this.request.readyState; } AjaxRequest.prototype.getStatus?=?function()?{ ??return?this.request.status; } AjaxRequest.prototype.getResponseText?=?function()?{ ??return?this.request.responseText; } AjaxRequest.prototype.getResponseXML?=?function()?{ ??return?this.request.responseXML; }這個例子中request 為什么不要用var 定義。