/* 封裝ajax函數(shù)
 * @param {string}opt.type http連接的方式，包括POST和GET兩種方式
 * @param {string}opt.url 發(fā)送請求的url
 * @param {boolean}opt.async 是否為異步請求，true為異步的，false為同步的
 * @param {object}opt.data 發(fā)送的參數(shù)，格式為對象類型
 * @param {function}opt.success ajax發(fā)送并接收成功調(diào)用的回調(diào)函數(shù)
 */
  function ajax(opt) {
    opt = opt || {};
    opt.method = opt.method.toUpperCase() || 'POST';
    opt.url = opt.url || '';
    opt.async = opt.async || true;
    opt.data = opt.data || null;
    opt.success = opt.success || function () {};
    opt.dataType = opt.dataType || "json";
    var xmlHttp = null;
    if (XMLHttpRequest) {
      xmlHttp = new XMLHttpRequest();
    }
    else {
      xmlHttp = new ActiveXObject('Microsoft.XMLHTTP');
    }var params = [];
    for (var key in opt.data){
      params.push(key + '=' + opt.data[key]);
    }
    var postData = params.join('&');
    if (opt.method.toUpperCase() === 'POST') {
      xmlHttp.open(opt.method, opt.url, opt.async);
      xmlHttp.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded;charset=utf-8');
      xmlHttp.send(postData);
    }
    else if (opt.method.toUpperCase() === 'GET') {
      xmlHttp.open(opt.method, opt.url + '?' + postData, opt.async);
      xmlHttp.send(null);
    } 
    xmlHttp.onreadystatechange = function () {
      if(opt.dataType != 'jsonp'){
        if (xmlHttp.readyState == 4 && xmlHttp.status == 200) {
          opt.success(xmlHttp.responseText);
        }
      }else{
        //alert(1); 
        if (xmlHttp.readyState == 4 && xmlHttp.status == 200) {
          var oScript = document.createElement('script');
          document.body.appendChild(oScript);

          var callbackname = 'wangxiao'
          oScript.src = opt.url + "?" + postData+'&callback='+callbackname;

          window['wangxiao'] = function(data) {
            opt.success(data);
            document.body.removeChild(oScript);
          };
        }


      }

    };
  }
  export default ajax;