text: export default (type='GET', url='', data={}, async=true) => {
  	return new Promise((resolve, reject) => { //定义一个promise
  		type = type.toUpperCase();
  
  		let requestObj;
  		if (window.XMLHttpRequest) {
  			requestObj = new XMLHttpRequest();
  		} else {
  			requestObj = new ActiveXObject;
  		}
  
  		if (type == 'GET') {
        let dataStr = ''; //数据拼接字符串
        Object.keys(data).forEach(key => {
          dataStr += key + '=' + data[key] + '&'
        })
  			dataStr = dataStr.substr(0, dataStr.lastIndexOf('&'));
  			url = url + '?' + dataStr;
  			requestObj.open(type, url, async);
  			requestObj.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
  			requestObj.send();
  		}else if (type == 'POST') {
  			requestObj.open(type, url, async);
  			requestObj.setRequestHeader("Content-type", "application/json");
  			requestObj.send(JSON.stringify(data));
  		}else {
  			reject('error type');
  		}
  
  		requestObj.onreadystatechange = () => {
  			if (requestObj.readyState == 4) {
  				if (requestObj.status == 200) {
  					let obj = requestObj.response
  					if (typeof obj !== 'object') {
  						obj = JSON.parse(obj);
  					}
  					resolve(obj);
  				}else {
  					reject(requestObj);
  				}
  			}
  		}
  	})
  }
  