//创建XMLHttpRequest对象的三种方法
1 var xhr = createXMLHttpRequest(); 2 function createXMLHttpRequest(){ 3 try{ return new XMLHttpRequest(); 5 }catch(e){ 6 try{ 7 return new ActiveXObject("Microsoft.XMLHTTP"); 8 }catch(e){ 9 try{10 return new ActiveXObject("Msxml2.XMLHTTP");11 }catch(e){ 12 alert("create XMLHTTPRequest object error!");13 }14 }15 }16 }17