仿jq封装ajax

/**
 * 封装ajax
 */
function ajax () {
  var ajaxData = {
    type: arguments[0].type || ‘GET‘,
    url: arguments[0].url || ‘‘,
    async: arguments[0].async || ‘true‘,
    data: arguments[0].data || null,
    dataType: arguments[0].dataType || ‘text‘,
    contentType: arguments[0].contentType || ‘application/x-www-form-urlencoded‘,
    beforeSend: arguments[0].beforeSend || function () { },
    success: arguments[0].success || function () { },
    error: arguments[0].error || function () { }
  }
  ajaxData.beforeSend()
  var xhr = createxmlHttpRequest()
  xhr.responseType = ajaxData.dataType
  xhr.open(ajaxData.type, ajaxData.url, ajaxData.async)
  xhr.setRequestHeader(‘Content-Type‘, ajaxData.contentType)
  xhr.send(convertData(ajaxData.data))
  xhr.onreadystatechange = function () {
    if (xhr.readyState == 4) {
      if (xhr.status == 200) {
        ajaxData.success(xhr.response)
      } else {
        ajaxData.error()
      }
    }
  }
}

function createxmlHttpRequest () {
  if (window.ActiveXObject) {
    return new ActiveXObject(‘Microsoft.XMLHTTP‘)
  } else if (window.XMLHttpRequest) {
    return new XMLHttpRequest()
  }
}

function convertData (data) {
  if (typeof data === ‘object‘) {
    var convertResult = ‘‘
    for (var c in data) {
      convertResult += c + ‘=‘ + data[c] + ‘&‘
    }
    convertResult = convertResult.substring(0, convertResult.length - 1)
    return convertResult
  } else {
    return data
  }
}