原生ajax請求與Promise請求

// 簡單的ajax原生實現var url = 'https://hq.tigerbrokers.com/fundamental/finance_calendar/getType/2017-02-26/2017-06-10';var result;var XHR = new XMLHttpRequest();XHR.open('GET', url, true);XHR.send();XHR.onreadystatechange = function() {    if (XHR.readyState == 4 && XHR.status == 200) {        result = XHR.response;        console.log(result);    }}var url = 'https://hq.tigerbrokers.com/fundamental/finance_calendar/getType/2017-02-26/2017-06-10';// 封裝一個get請求的方法function getJSON(url) {    return new Promise(function(resolve, reject) {        var XHR = new XMLHttpRequest();        XHR.open('GET', url, true);        XHR.send();        XHR.onreadystatechange = function() {            if (XHR.readyState == 4) {                if (XHR.status == 200) {                    try {                        var response = JSON.parse(XHR.responseText);                        resolve(response);                    } catch (e) {                        reject(e);                    }                } else {                    reject(new Error(XHR.statusText));                }            }        }    })}getJSON(url).then(res => console.log(res));