Promise封装XMLHttpRequest

[mtonhuang]

// tools.js
/* 封装 XMLHttpRequest*/
// 序列化参数
function serialize(data) {
  if (!data) return "";
  var pairs = [];
  for (var name in data) {
    if (!data.hasOwnProperty(name)) continue;
    if (typeof data[name] === "function") continue;
    var value = data[name].toString();
    name = encodeURIComponent(name);
    value = encodeURIComponent(value);
    pairs.push(name + "=" + value);
  }
  return pairs.join("&");
}
// 创 Ajax 请求对象，兼容ie8，ie9
function XHR() {
  var xObj;
  if (window.XMLHttpRequest) {
    xObj = new XMLHttpRequest();
  } else if (window.ActiveXObjext) {
    xObj = new ActiveXObject();
  }
  return xObj;
}
// 封装
const ajaxForPromise = function(params) {
  var data = params.data;
  var url = params.url;
  var method = params.method || "GET";
  var responseType = params.responseType || "json";
  var setHeader = params.setHeader;
  var open = params.open || true;
  return new Promise((resolve, reject) => {
    // promise封装
    var xhr = XHR();
    var params = null;
    xhr.onreadystatechange = handler;
    if (method.toUpperCase() === "GET") {
      url = url + "?" + serialize(data);
    } else if (method.toUpperCase() === "POST") {
      params = serialize(data);
    }
    xhr.open(method, url, open);
    if (setHeader) {
      xhr.setRequestHeader(
        "Content-type",
        "application/x-www-form-urlencoded;charset=UTF-8"
      );
    }
    xhr.responseType = responseType;
    xhr.send(params);

    function handler() {
      if (this.readyState !== 4) {
        return;
      }
      if (this.status === 200) {
        resolve(this.response); // 正确回调
      } else {
        reject(new Error(this.statusText)); // 错误回调
      }
    }
  });
};
export {
  ajaxForPromise
};