localStorage的简单封装

const Storage = (function(){
    return{
        set:function(key,value,expireSeconds){
            localStorage[key] = JSON.stringify({
                value,
                expired:expireSeconds === undefined ? undefined :Date.now() + 1000*expireSeconds
            })
        },
        get:function(key){
            if(localStorage[key] === undefined){
                return
            }
            let object = JSON.parse(localStorage[key])
            if(object.expired === undefined || Date.now() < object.expired){
                return object.value
            }else{
                delete localStorage[key]
            }
        }
    }
})()