ajax.js

function ajax(url, method = "get", param = {}) {
  return new Promise((resolve, reject) => {
    const xhr = new XMLHttpRequest();
    const paramString = getStringParam(param);
    if (method === "get" && paramString) {
      url.indexOf("?") > -1 ? (url += paramString) : (url += `?${paramString}`);
    }
    xhr.open(method, url);
    xhr.onload = function() {
      const result = {
        status: xhr.status,
        statusText: xhr.statusText,
        headers: xhr.getAllResponseHeaders(),
        data: xhr.response || xhr.responseText
      };
      if ((xhr.status >= 200 && xhr.status < 300) || xhr.status == 304) {
        resolve(result);
      } else {
        reject(result);
      }
    };
    // 设置请求头
    xhr.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
    // 跨域携带cookie
    xhr.withCredentials = true;
    // 错误处理
    xhr.onerror = function() {
      reject(new TypeError("请求出错"));
    };
    xhr.timeout = function() {
      reject(new TypeError("请求超时"));
    };
    xhr.onabort = function() {
      reject(new TypeError("请求被终止"));
    };
    if (method === "post") {
      xhr.send(paramString);
    } else {
      xhr.send();
    }
  });
}

function getStringParam(param) {
  let dataString = "";
  for (const key in param) {
    dataString += `${key}=${param[key]}&`;
  }
  return dataString;
}