npm-polymer-elements/iron-localstorage/README.md

Polymer Elements package for npm

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_[Demo and API Docs](https://elements.polymer-project.org/elements/iron-localstorage)_


##&lt;iron-localstorage&gt;


Element access to Web Storage API (window.localStorage).

Keeps `value` property in sync with localStorage.

Value is saved as json by default.

### Usage:

`ls-sample` will automatically save changes to its value.

    <dom-module id="ls-sample">
      <iron-localstorage name="my-app-storage"
        value="{{cartoon}}"
        on-iron-localstorage-load-empty="initializeDefaultCartoon"
      ></iron-localstorage>
    </dom-module>

    <script>
      Polymer({
        is: 'ls-sample',
        properties: {
          cartoon: {
            type: Object
          }
        },
        // initializes default if nothing has been stored
        initializeDefaultCartoon: function() {
          this.cartoon = {
            name: "Mickey",
            hasEars: true
          }
        },
        // use path set api to propagate changes to localstorage
        makeModifications: function() {
          this.set('cartoon.name', "Minions");
          this.set('cartoon.hasEars', false);
        }
      });
    </script>

### Tech notes:

* `value.*` is observed, and saved on modifications. You must use
    path change notifification methods such as `set()` to modify value
    for changes to be observed.

* Set `auto-save-disabled` to prevent automatic saving.

* Value is saved as JSON by default.

* To delete a key, set value to null

Element listens to StorageAPI `storage` event, and will reload upon receiving it.

**Warning**: do not bind value to sub-properties until Polymer
[bug 1550](https://github.com/Polymer/polymer/issues/1550)
is resolved. Local storage will be blown away.
`<iron-localstorage value="{{foo.bar}}"` will cause **data loss**.