paper-input-char-counter.html

<!--
@license
Copyright (c) 2015 The Polymer Project Authors. All rights reserved.
This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
Code distributed by Google as part of the polymer project is also
subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
-->

<link rel="import" href="../polymer/polymer.html">
<link rel="import" href="../paper-styles/typography.html">
<link rel="import" href="paper-input-addon-behavior.html">

<!--
`<paper-input-char-counter>` is a character counter for use with `<paper-input-container>`. It
shows the number of characters entered in the input and the max length if it is specified.

    <paper-input-container>
      <input is="iron-input" maxlength="20">
      <paper-input-char-counter></paper-input-char-counter>
    </paper-input-container>

### Styling

The following mixin is available for styling:

Custom property | Description | Default
----------------|-------------|----------
`--paper-input-char-counter` | Mixin applied to the element | `{}`
-->

<dom-module id="paper-input-char-counter">
  <template>
    <style>
      :host {
        display: inline-block;
        float: right;

        @apply(--paper-font-caption);
        @apply(--paper-input-char-counter);
      }

      :host([hidden]) {
        display: none !important;
      }

      :host-context([dir="rtl"]) {
        float: left;
      }
    </style>

    <span>[[_charCounterStr]]</span>
  </template>
</dom-module>

<script>
  Polymer({
    is: 'paper-input-char-counter',

    behaviors: [
      Polymer.PaperInputAddonBehavior
    ],

    properties: {
      _charCounterStr: {
        type: String,
        value: '0'
      }
    },

    /**
     * This overrides the update function in PaperInputAddonBehavior.
     * @param {{
     *   inputElement: (Element|undefined),
     *   value: (string|undefined),
     *   invalid: boolean
     * }} state -
     *     inputElement: The input element.
     *     value: The input value.
     *     invalid: True if the input value is invalid.
     */
    update: function(state) {
      if (!state.inputElement) {
        return;
      }

      state.value = state.value || '';

      var counter = state.value.toString().length.toString();

      if (state.inputElement.hasAttribute('maxlength')) {
        counter += '/' + state.inputElement.getAttribute('maxlength');
      }

      this._charCounterStr = counter;
    }
  });
</script>