LocalStorageCache

LocalStorageCache.js

var cache = (function() {
    'use strict';
    var TTL_POSTFIX = 'time2live';
    var TTE_POSTFIX = 'time2expire';
    function _hasLocalStorage() {
        if (!window.localStorage) {
            throw new Error('you have no localStorage');
        }
    }
    function _removeCachedKey(key) {
        localStorage.removeItem(key);
        localStorage.removeItem(key+TTE_POSTFIX);
        localStorage.removeItem(key+TTL_POSTFIX);
    }
    function addItem(key,value,expireAfter,removeAfter) {
        _hasLocalStorage();
        localStorage.setItem(key,value);
        if (expireAfter > removeAfter) {
            throw new Error('Expire after have to be less then removeAfter');
        }
        localStorage.setItem(key+TTE_POSTFIX, +new Date() + 1000 * 60 * 60 * expireAfter);
        localStorage.setItem(key+TTL_POSTFIX, +new Date() + 1000 * 60 * 60 * removeAfter);
    }

    function getItem(key) {
        _hasLocalStorage();
        var ttl = parseInt(localStorage.getItem(key+TTL_POSTFIX));
        var tte = parseInt(localStorage.getItem(key+TTE_POSTFIX));
 
        var value = localStorage.getItem(key);
        
        if (+new Date() > tte) {
            return {value: value, expired: false};
        }
        else if (+new Date() < ttl) {
            return {value:value, expired: true};
        }
        else {
            _removeCachedKey(key);
            return null;
        }
    }

    return {
        addItem:addItem,
        getItem:getItem
    };

}());