bhanu bhanu - 4 months ago 106
Javascript Question

Preselect a default page in iron-pages when using with paper-tabs

I am using Polymer

iron-pages
along with
paper-tabs
in my rails app. The problem is none of pages were shown until one of the
paper-tabs
was clicked. I want the first page in
iron-pages
to be selected by default without user interaction.

I have put both
paper-tabs
and
iron-pages
in a
<template is='dom-bind'></template>
. Have read documentation about data binding, But I couldn't figure out how to achieve this. Please somebody suggest your valuable suggestions. Thank you.

<template is="dom-bind">
<div class="middle">
<paper-tabs class="bottom self-end" selected="{{selected}}">
<paper-tab>Page 1</paper-tab>
<paper-tab>Page 2</paper-tab>
</paper-tabs>
</div>
<div class="bottom">
<iron-pages selected="{{selected}}">
<div> Page 1(This should be selected by default.)
</div>
<div> Page 2
</div>
</iron-pages>
</div>
</template>

Answer

Since you're working with an auto-binding template, simply add a short script that sets the selected property of your <iron-pages> element at load time. For example (assuming you are using webcomponents-lite.js):

<template is="dom-bind">
  <div class="middle">
    <paper-tabs class="bottom self-end" selected="{{selected}}">
      <paper-tab>Page 1</paper-tab>
      <paper-tab>Page 2</paper-tab>
    </paper-tabs>
  </div>
  <div class="bottom">
    <iron-pages selected="{{selected}}">
      <div> Page 1 (This will be selected by default.)
      </div>
      <div> Page 2
      </div>
    </iron-pages>
  </div>
</template>

<script>
  document.addEventListener('WebComponentsReady', function () {
    var template = document.querySelector('template[is="dom-bind"]');
    template.selected = 0; // selected is an index by default
  });
</script>