function setCookie (key, value, expiredays) {
  let exdate = new Date()
  if (expiredays) {
    exdate.setDate(exdate.getDate() + expiredays)
    document.cookie = key + '=' + encodeURI(value) + ((expiredays === null) ? '' : ';expires=' + exdate.toGMTString()) + ';path=/'
  } else {
    document.cookie = key + '=' + encodeURI(value) + ';path=/'
  }
}

function getCookie (key) {
  let name = key + '='
  let ca = document.cookie.split(';')
  for (let i = 0; i < ca.length; i++) {
    let c = ca[i].trim()
    if (c.indexOf(name) === 0) return decodeURI(c.substring(name.length, c.length))
  }
  return null
}

function removeCookie(key) {
  this.setCookie(key, '', -1)
}