PolymerElements/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,

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>
  <head>
    <script type="module">
      import '@polymer/polymer/lib/elements/dom-bind.js';
      import '@polymer/iron-ajax/iron-ajax.js';
      import '@polymer/app-storage/app-indexeddb-mirror/app-indexeddb-mirror.js';
    </script>
  </head>
  <body>
    <dom-bind>
      <template>
        <iron-ajax
            url="/api/cats"
            handle-as="json"
            last-response="{{liveData}}">
        </iron-ajax>
        <app-indexeddb-mirror
            key="cats"
            data="{{liveData}}"
            persisted-data="{{persistedData}}">
        </app-indexeddb-mirror>

        <dom-repeat>
          <template items="{{persistedData}}" as="cat">
            <div>[[cat.name]]</div>
          </template>
        </dom-repeat>
      </template>
    </dom-bind>
  </body>
</html>

<app-localstorage-document>

<html>
  <head>
    <script type="module">
      import '@polymer/polymer/lib/elements/dom-bind.js';
      import '@polymer/paper-input/paper-input.js';
      import '@polymer/app-storage/app-localstorage-document/app-localstorage-document.js';
    </script>
  </head>
  <body>
    <dom-bind>
      <template>
        <paper-input value="{{search}}"></paper-input>
        <app-localstorage-document key="search" data="{{search}}">
        </app-localstorage-document>
      </template>
    </dom-bind>
  </body>
</html>

In a Polymer 3 element

AppStorageBehavior

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

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>

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`
      <iron-ajax
          url="/api/cats"
          handle-as="json"
          last-response="{{liveData}}">
      </iron-ajax>
      <app-indexeddb-mirror
          key="cats"
          data="{{liveData}}"
          persisted-data="{{persistedData}}">
      </app-indexeddb-mirror>

      <template is="dom-repeat" items="{{persistedData}}" as="cat">
        <div>[[cat.name]]</div>
      </template>
    `;
  }
}
customElements.define('sample-element', SampleElement);

<app-localstorage-document>

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`
      <paper-input value="{{search}}"></paper-input>
      <app-localstorage-document key="search" data="{{search}}">
      </app-localstorage-document>
    `;
  }
}
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

git clone https://github.com/PolymerElements/app-storage
cd app-storage
npm install
npm install -g polymer-cli

Running the demo locally

polymer serve --npm
open http://127.0.0.1:<port>/demo/

Running the tests

polymer test --npm