[](https://www.npmjs.com/package/@polymer/iron-checked-element-behavior) [](https://travis-ci.org/PolymerElements/iron-checked-element-behavior) [](https://webcomponents.org/element/@polymer/iron-checked-element-behavior) ## IronCheckedElementBehavior 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](https://www.webcomponents.org/element/@polymer/iron-checked-element-behavior), [Demo](https://www.webcomponents.org/element/@polymer/iron-checked-element-behavior/demo/demo/index.html). ## Usage ### Installation ``` npm install --save @polymer/iron-checked-element-behavior ``` ### In a Polymer 3 element ```js 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` validate {{label}} `; } static get properties() { return {label: {type: String, value: 'not validated'}}; } _checkValidity() { this.validate(); this.label = this.invalid ? 'is invalid' : 'is valid'; } } customElements.define('simple-checkbox', SimpleCheckbox); ``` ## Contributing If you want to send a PR to this element, here are the instructions for running the tests and demo locally: ### Installation ```sh git clone https://github.com/PolymerElements/iron-checked-element-behavior cd iron-checked-element-behavior npm install npm install -g polymer-cli ``` ### Running the demo locally ```sh polymer serve --npm open http://127.0.0.1:/demo/ ``` ### Running the tests ```sh polymer test --npm ```