JavaScript ajax 封装

function ajax(setting) {
  var ajax = new XMLHttpRequest();
  // 默认 get
  if (!setting.method) setting.method = 'get';

  // 组合data查询数据
  if (setting.data) {
    setting.data = getSearch(setting.data);
  } else {
    setting.data = '';
  }

  if (setting.method.toLowerCase() == 'get') {
    ajax.open('get', setting.url + '?' + setting.data, true);
    ajax.send();
  } else if (setting.method.toLowerCase() == 'post') {
    ajax.open('post', setting.url, true);
    ajax.setRequestHeader('Content-type', 'appliction/x-www-form-urlencoded');
    ajax.send(setting.data);
  }

  ajax.onreadystatechange = function () {
    if (ajax.readyState == 4) {
      if (ajax.status == 200) {
        setting.success(ajax.responseText);
      } else {
        console.log('Error:' + ajax.status);
      }
    }
  };
}

// 拼接字符串
function getSearch(obj) {
  var str = '';
  for (var key in obj) {
    str += key + '=' + obj[key] + '&';
  }
  return str.slice(0, str.length - 1);
}