关于前端:XMLHttpRequest-封装

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封裝：

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);
                }
            }
        }
    })
}

应用：