Implements an element that has a checked attribute and can be added to a form
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Latest commit 64c9511 Sep 14, 2018

Published on NPM Build status Published on


Use IronCheckedElementBehavior to implement a custom element that has a checked property, which can be used for validation if the element is also required. Element instances implementing this behavior will also be registered for use in an iron-form element.

See: Documentation, Demo.



npm install --save @polymer/iron-checked-element-behavior

In a Polymer 3 element

import {PolymerElement} from '@polymer/polymer/polymer-element.js';
import {mixinBehaviors} from '@polymer/polymer/lib/legacy/class.js';
import {html} from '@polymer/polymer/lib/utils/html-tag.js';

import {IronCheckedElementBehavior} from '../iron-checked-element-behavior.js';

class SimpleCheckbox extends mixinBehaviors(IronCheckedElementBehavior, PolymerElement) {
  static get template() {
    return html`
        :host([invalid]) {
          color: red;

      <button on-click="_checkValidity">validate</button>
      <input type="checkbox" id="checkbox" checked="{{checked::input}}">
      <span id="labelText">{{label}}</span>

  static get properties() {
    return {label: {type: String, value: 'not validated'}};

  _checkValidity() {
    this.label = this.invalid ? 'is invalid' : 'is valid';

customElements.define('simple-checkbox', SimpleCheckbox);


If you want to send a PR to this element, here are the instructions for running the tests and demo locally:


git clone
cd iron-checked-element-behavior
npm install
npm install -g polymer-cli

Running the demo locally

polymer serve --npm

Running the tests

polymer test --npm