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amp-list

Introduction

The amp-list enables client-side rendering in AMP. Content can either be fetched from a JSON endpoint or locally from amp-state.

Setup

Import the amp-list component ...

<script async custom-element="amp-list" src="https://cdn.ampproject.org/v0/amp-list-0.1.js"></script>

... and the amp-mustache component in the header.

<script async custom-template="amp-mustache" src="https://cdn.ampproject.org/v0/amp-mustache-0.2.js"></script>

Import the amp-bind component for dynamically changing the content of an amp-list.

<script async custom-element="amp-bind" src="https://cdn.ampproject.org/v0/amp-bind-0.1.js"></script>

Basic usage

The amp-list content is provided by a JSON CORS endpoint, which is defined by the src attribute. The URL's protocol must be HTTPS. The response must be a JSON object containing an array property items, for example:

{
  "items": [
    {
      "title": "amp-carousel",
      "url": "https://ampbyexample.com/components/amp-carousel"
    },
    ...
  ]
}

The list content is rendered via an amp-mustache template. The template can be specified either by id, or by using a nested element. For performance reasons, we're adding binding="no" as we're not using amp-bind.

<amp-list layout="fixed-height"
  height="100"
  src="/static/samples/json/examples.json"
  binding="no">
  <template type="amp-mustache">
    <div><a href="{{url}}">{{title}}</a></div>
  </template>
</amp-list>

Re-using an existing template

The template can also be specified using an ID of an existing template element.

<template type="amp-mustache"
  id="amp-template-id">
  <div><a href="{{url}}">{{title}}</a></div>
</template>
<amp-list layout="fixed-height"
  height="100"
  src="/static/samples/json/examples.json"
  template="amp-template-id"
  binding="no">
</amp-list>

Handling list overflow

If the amp-list content requires more space than available, the AMP runtime will display the overflow element (if specified).

Show more
<amp-list layout="fixed-height"
  height="48"
  src="/static/samples/json/examples.json"
  binding="no">
  <div overflow
    role="button"
    aria-label="Show more"
    class="list-overflow">
    Show more
  </div>
  <template type="amp-mustache">
    <div><a href="{{url}}">{{title}}</a></div>
  </template>
</amp-list>

Dynamic src

The content of an amp-list can be changed dynamically by modifying it's src value using amp-bind.

<amp-list layout="fixed-height"
  height="100"
  src="/static/samples/json/examples.json"
  [src]="srcUrl"
  binding="no">
  <template type="amp-mustache">
    <div><a href="{{url}}">{{title}}</a></div>
  </template>
</amp-list>
<button on="tap:AMP.setState({ srcUrl: '/static/samples/json/examples2.json' })">Change source</button>

Rendering amp-state

This sample shows off one of amp-list's most powerful features: being able to directly render objects from amp-state, This is possible by binding the results of an amp-bind expression to the src attribute: [src]="items". To make sure that the amp-list resizes accordingly, we dynamically calculate the height based on the number of list elements: [height]="items.length * 22". The initial state (an empty list) is defined in an amp-state element.

amp-bind expressions are not evaluated on page load, but only after an user interaction has taken place. Initial amp-list content still needs to be fetched from a JSON endpoint.

<amp-state id="items">
  <script type="application/json">
    []
  </script>
</amp-state>
<amp-list layout="fixed-height"
  height="0"
  [src]="items"
  [height]="items.length * 22"
  single-item
  items="."
  binding="no">
  <template type="amp-mustache">
    <div>{{ . }}</div>
  </template>
</amp-list>
<button on="tap:AMP.setState({ items: items.splice(items.length, 0, 'item ' + items.length) })">
  Add item
</button>

Empty list content

If the list contains an empty array, you can use mustache inverted sections to print a message.

For this to work, we have to use the single-item attribute and items attribute to be able to access the root items array inside the template.

<amp-list layout="fixed-height"
  height="100"
  src="/static/samples/json/examples-empty.json"
  [src]="emptyListSampleSrc || '/static/samples/json/examples-empty.json'"
  single-item
  items="."
  reset-on-refresh
  binding="no">
  <template type="amp-mustache">
    {{#items}}
      <div><a href="{{url}}">{{title}}</a></div>
    {{/items}}
    {{^items}}
      <div>No items founds.</div>
    {{/items}}
  </template>
</amp-list>
<button on="tap:AMP.setState({ emptyListSampleSrc: '/static/samples/json/examples.json' })">
  Add items
</button>

Using a placeholder

You can use a custom placeholder that looks similar to the rendered items to improve the user experience while the list is loading. We are using an endpoint which intentionally delays the response by 10 seconds.

Loading...
Loading...
Loading...
<amp-list id="amp-list-placeholder"
  noloading
  layout="fixed-height"
  height="654"
  src="/documentation/examples/api/slow-json-with-items/?delay=10000"
  binding="no">
  <div placeholder>
    <div class="product">
      <div class="image-placeholder"></div>
      <div>Loading...</div>
    </div>
    <div class="product">
      <div class="image-placeholder"></div>
      <div>Loading...</div>
    </div>
    <div class="product">
      <div class="image-placeholder"></div>
      <div>Loading...</div>
    </div>
  </div>
  <template type="amp-mustache">
    <div class="product">
      <amp-img width="150"
        height="100"
        alt="{{name}}"
        src="{{img}}"></amp-img>
      <div>
        <div>{{name}}</div>
        <div>{{{stars}}}</div>
        <div>${{price}}</div>
      </div>
    </div>
  </template>
</amp-list>

Triggering refresh

You can use the refresh action to trigger a refresh on amp-list. Notice how we are using reset-on-refresh attribute to ensure that the placeholder is reloaded.

<button on="tap:myAmpList.refresh">Refresh list</button>
<amp-list id="myAmpList"
  reset-on-refresh
  layout="fixed-height"
  height="600"
  src="/documentation/examples/api/slow-json-with-items/?delay=1000"
  binding="no">
  <template type="amp-mustache">
    <div class="product">
      <amp-img width="150"
        height="100"
        alt="{{name}}"
        src="{{img}}"></amp-img>
      <div>
        <div>{{name}}</div>
        <div>{{{stars}}}</div>
        <div>${{price}}</div>
      </div>
    </div>
  </template>
</amp-list>
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