localstorge 存储数据。设定过期时间
// 存储到localstorage 半小时
function setlocalStorage(year,range,data){
var date = new Date().getTime()
var key = 'data' + year + range
var storage = window.localStorage;

var obj = {key:data,'time':date}
localStorage.setItem(key, JSON.stringify(obj))
}
// 判断是否过期半小时
function judgelocalStorage(year,range){
var date = new Date().getTime()
var key = 'data' + year + range
var storage = window.localStorage;
if(JSON.parse(localStorage.getItem(key))){
if(date - JSON.parse(localStorage.getItem(key)).time > 1800000){
storage.removeItem(key)
return null
} else {
return JSON.parse(storage.getItem(key)).key
}
} else {
return null
}