js設定cookie有效期，并擷取存儲的cookie值

// 設定cookie，setTime是用來設定有效期，下邊代碼expires為30時代表有效期30分鐘
  setCookie: function (cname, value, expires) {
    let date = new Date()
    date.setTime(date.getTime() + expires * 60 * 1000)
    document.cookie = cname + '=' + escape(value) + ';expires=' + date.toUTCString()
  },
  // 擷取cookie，傳入key以擷取value
  getCookie: function (cname) {
    if (document.cookie.length > 0) {
      let cstart = document.cookie.indexOf(cname + '=')
      if (cstart !== -1) {
        cstart = cstart + cname.length + 1
        let cend = document.cookie.indexOf(';', cstart)
        if (cend === -1) {
          cend = document.cookie.length
        }
        return unescape(document.cookie.substring(cstart, cend))
      }
    }
    return ''
  },