获得url？后的参数

export function getQueryString(name) {
  let reg = new RegExp(`(^|&)${name}=([^&]*)(&|$)`, 'i');
  let r = window.location.search.substr(1).match(reg);
  if (r != null) {
    return unescape(r[2]);
  }
  return null;
}