文章标题

• Ajax过程？
  
  1. new xhr：new XMLHttpRequest(); || new ActiveXObject(“Microsoft.XMLHTTP”);
  2. xhr.open(method,url,async);
  3. xhr.send();
  4. xhr.onreadystatechange = function(){
     if(xhr.readyState==4&&xhr.status==200){
     var result = xhr.responseText;
     };