[](https://www.npmjs.com/package/@polymer/app-storage) [](https://travis-ci.org/PolymerElements/app-storage) [](https://webcomponents.org/element/@polymer/app-storage) ## App-Storage These are a set of behaviors and elements that make it easy to synchronize in-memory data to persistant storage systems. See: [Documentation](https://www.webcomponents.org/element/@polymer/app-storage), ### AppStorageBehavior `AppStorageBehavior` is an abstract behavior that makes it easy to synchronize in-memory data and a persistant storage system, such as the browser's IndexedDB, or a remote database like Firebase. ### AppNetworkStatusBehavior `AppNetworkStatusBehavior` tracks the status of whether the browser is online or offline. True if the browser is online, and false if the browser is offline matching the HTML browser state spec. ### <app-indexeddb-mirror> `app-indexeddb-mirror` is a purpose-built element to easily add read-only offline access of application data that is typically only available when the user is connected to the network. When an app using this element is connected to the network, the element acts as a pass-through for live application data. Data is bound into the `data` property, and consumers of the data can bind to the correlated `persistedData` property. As live data changes, `app-indexeddb-mirror` caches a copy of the live data in a local IndexedDB database. When the app is no longer connected to the network, `app-indexeddb-mirror` toggles its `persistedData` property to refer to a read-only copy of the corresponding data in IndexedDB. This element is particularly useful in cases where an API or storage layer (such as Firebase, for example) does not support caching data for later use during user sessions that begin while the user is disconnected from the network. ### <app-localstorage-document> app-localstorage-document synchronizes storage between an in-memory value and a location in the browser's localStorage system. localStorage is a simple and widely supported storage API that provides both permanent and session-based storage options. Using app-localstorage-document you can easily integrate localStorage into your app via normal Polymer databinding. app-localstorage-document is the reference implementation of an element that uses `AppStorageBehavior`. Reading its code is a good way to get started writing your own storage element. ## Usage ### Installation ``` npm install --save @polymer/app-storage ``` ### In an html file #### <app-indexeddb-mirror> ```html ``` #### <app-localstorage-document> ```html ``` ### In a Polymer 3 element #### AppStorageBehavior ```js import {PolymerElement, html} from '@polymer/polymer'; import {mixinBehaviors} from '@polymer/polymer/lib/legacy/class.js'; import {AppStorageBehavior} from '@polymer/app-storage/app-storage-behavior.js'; class SampleElement extends mixinBehaviors([AppStorageBehavior], PolymerElement) { get isNew() { return /* your override here */ } get zeroValue() { return /* your override here */ } get saveValue() { return /* your override here */ } reset() { /* your optional override here */ } getStoredValue() { /* your override here */ } setStoredValue() { /* your override here */ } } customElements.define('sample-element', SampleElement); ``` #### Polymer.AppNetworkStatusBehavior ```js import {PolymerElement, html} from '@polymer/polymer'; import {mixinBehaviors} from '@polymer/polymer/lib/legacy/class.js'; import {AppNetworkStatusBehavior} from '@polymer/app-storage/app-network-status-behavior.js'; class SampleElement extends mixinBehaviors([AppNetworkStatusBehavior], PolymerElement) { alertNetworkStatus() { alert(`I am ${this.online ? 'online' : 'offline'}!`) } } customElements.define('sample-element', SampleElement); ``` #### <app-indexeddb-mirror> ```js import {PolymerElement, html} from '@polymer/polymer'; import '@polymer/iron-ajax/iron-ajax.js'; import '@polymer/app-storage/app-indexeddb-mirror/app-indexeddb-mirror.js'; class SampleElement extends PolymerElement { static get template() { return html` `; } } customElements.define('sample-element', SampleElement); ``` ##### <app-localstorage-document> ```js import {PolymerElement, html} from '@polymer/polymer'; import '@polymer/paper-input/paper-input.js'; import '@polymer/app-storage/app-localstorage-document/app-localstorage-document.js'; class SampleElement extends PolymerElement { static get template() { return html` `; } } customElements.define('sample-element', SampleElement); ``` ## Contributing If you want to send a PR to this element, here are the instructions for running the tests and demo locally: ### Installation ```sh git clone https://github.com/PolymerElements/app-storage cd app-storage npm install npm install -g polymer-cli ``` ### Running the demo locally ```sh polymer serve --npm open http://127.0.0.1:/demo/ ``` ### Running the tests ```sh polymer test --npm ```