200Puls / iron-lazy-pages

Lazy-load content and lazy-register pages to reduce the first load time

iron-lazy-pages

<iron-pages> with lazy-loading functionality.

Looking for 3.0-preview version of this element? Check out issue 63

Lazy-loading pages

Big applications have a lot of pages. On first load, loading all page elements is undesirable. Most of the pages are unused for the current user. To solve these performance issues, lazy-loading provides an easy-to-use solution.

Lazy-loading means that all elements of your page are loaded when the user opens the respective page. E.g. when your user visits domain.com/about, all elements on the about page are fetched and loaded.

Example:

<iron-lazy-pages attr-for-selected="data-route" selected="{{route}}">
  <x-foo data-route="foo" data-path="demo/x-foo.html"></x-foo>
  <x-bar data-route="bar" data-path="demo/x-bar.html"></x-bar>
  <section data-route="baz">
    Inline element baz.
  </section>
</iron-lazy-pages>

In the above example, whenever the user routes to domain.com/foo, the elements defined in foo/foo.html are fetched from the server and loaded by Polymer.

Consequently whenever the selected value changes from foo to bar, the page foo will be hidden.

Fetching is only performed once, e.g. switching from foo to bar to foo will fetch foo once and show foo twice.

<dom-if> support

You can also add <dom-if> as a route to enable restamping:

<iron-lazy-pages
    attr-for-selected="data-route"
    selected="{{route}}"
    loading="{{loading}}"
    hide-immediately>
  <template is="dom-if" data-route="foo" restamp>
    Leaving this tab and coming back will loose input value due to restamp<br/>
    <input type="text"/>
  </template>
  <template is="dom-if" data-route="bar">
    Leaving this tab and coming back will keep input value<br/>
    <input type="text"/>
  </template>
</iron-lazy-pages>