4.获取地址状态栏参数

const getUrlParam = (name) => {
    let reg = new RegExp('(^|&)' + name + '=([^&]*)(&|$)')
     if( !window.location.href.includes('?')) return
    let r = window.location.href.split("?")[1].match(reg)
    if (r != null) return unescape(r[2])
    return null
}
//备注:window.location.search有时候获取不到值, window.location.href.split("?")[1]等价于
//window.location.search.substr(1)
“(^|&)” + name + "=([^&]*)(&|$)的含义 :
  匹配以&name=开头或者空白name=开头中间为任意多个除了&以外的字符 一旦遇到& 
  或者空白就中止取值