一段封装好的ajax发送请求的js代码

var $ = {
  getpa:function(data){
    if(data && typeof data == "object"){
      var str = '?';
      for(var key in data){
        str = str + key + "="+data[key]+"&";
      }
      str = str.substr(0,str.length-1);
    }
    return str;
  },
  ajax:function(option){
    var type = option.type || 'get';
    var url = option.url || location.href;
    var data = this.getpa(option.data) || '';
    var success = option.success;
    var xhr = new XMLHttpRequest();
    if(type == "get"){
      url += data;
      data = null;
    }
    xhr.open(type,url);
    if(type == "post"){
      xhr.setRequestHeader("Content-Type","application/x-www-form-urlencoded");
    }
    xhr.send(data);
    xhr.onreadystatechange=function(){
      if(xhr.status==200&&xhr.readyState==4){
        var rh = xhr.getResponseHeader("Content-Type");
        if(rh.indexOf("xml") != -1){
          var result = xhr.responseXML;
        }else if(rh.lastIndexOf("json") != -1){
          var result = JSON.parse(xhr.responseText);
        }else{
          var result = xhr.responseText;
        }
        success&&success(result);
      }
    }
  }
}