Cache Class Helper Example

Cache.js

/**
 * docs: /docs/cache.md
 */
import LZUTF8 from 'lzutf8'
window.LZUTF8 = LZUTF8
let cache = { 'default': {} }

try{
    cache = JSON.parse( LZUTF8.decompress(localStorage.getItem('app_cache'), {inputEncoding: 'StorageBinaryString'}) )
    Object.keys(cache).forEach(groupName =>{
        const group = cache[groupName]
        Object.keys(group).forEach(itemKey =>{
            if(!group[itemKey].localStorage){
                delete cache[groupName][itemKey]
            }
        })
    })
}catch(error){}

export default class Cache{
    constructor () {
        this._group = 'default'
        this._localStorage = false
        this._expires = 60 * 60 * 1000 // default expiry is 1 hour
    }
    persistAcrossPageReload(enabled = true){
        this._localStorage = enabled
        return this
    }
    get(key, defaultValue = null){
        this._initGroupIfNoExist()
        const cacheItem = cache[this._group][key]
        if(cacheItem){
            if(!this._expired(cacheItem)) return cacheItem.value
            // if it is expired go ahead and clean it out of the cache here
            delete cache[this._group][key]
            this._syncLocalStorage()
        }

        return typeof defaultValue === 'function' ? defaultValue() : defaultValue
    }

    put(key, value){
        this._initGroupIfNoExist()
        cache[this._group][key] = {
            expires: Date.now() + this._expires,
            localStorage: this._localStorage,
            value
        }
        this._syncLocalStorage()
        return this
    }

    pull(key, defaultValue= null){
        const value = this.get(key, defaultValue)
        this.forget(key)
        this._syncLocalStorage()
        return value
    }

    has(key){
        return !! this.get(key)
    }

    remove(key){
        this.forget(key)
    }

    forget(key){
        if(cache[this._group] && cache[this._group][key]){
            delete cache[this._group][key]
            this._syncLocalStorage()
        }
        return this
    }

    flushGroup(group){
        cache[group] = {}
        this._syncLocalStorage()
        return this
    }
    flush(){
        cache = { 'default' : {} }
        this._syncLocalStorage()
        return this
    }

    group(name){
        this._group = name
        return this
    }

    expires(milliseconds){
        if(milliseconds !== null){
            this._expires = milliseconds
        }
        return this
    }

    getGroup(group){
        return cache[group] || {}
    }

    all(){
        return cache
    }
    _expired(item){
        return Date.now() > item.expires
    }
    _initGroupIfNoExist(){
        cache[this._group] = cache[this._group] || {}
    }
    _syncLocalStorage(){
        localStorage.setItem(
            'app_cache',
            LZUTF8.compress(JSON.stringify(cache), {outputEncoding: 'StorageBinaryString'})
        )
    }
}