微信小程序：设置setStorageSync本地缓存时间

var timestamp = Date.parse(new Date());
var expiration = timestamp + 1800000; //缓存30分钟
var data_expiration = wx.getStorageSync("data_expiration");
if (data_expiration) {
  if (timestamp > data_expiration) {
    wx.clearStorageSync()
    wx.setStorageSync("data_expiration", expiration)
  }
} else {
  wx.setStorageSync("data_expiration", expiration)
}