[](https://www.npmjs.com/package/@polymer/iron-validatable-behavior)
[](https://travis-ci.org/PolymerElements/iron-validatable-behavior)
[](https://webcomponents.org/element/@polymer/iron-validatable-behavior)
## IronValidatableBehavior
Use `IronValidatableBehavior` to implement an element that validates user input. By using this behaviour, your custom element will get a public `validate()` method, which
will return the validity of the element, and a corresponding `invalid` attribute,
which can be used for styling. Can be used alongside an element implementing
the `IronValidatableBehavior` behaviour.
See: [Documentation](https://www.webcomponents.org/element/@polymer/iron-validatable-behavior),
[Demo](https://www.webcomponents.org/element/@polymer/iron-validatable-behavior/demo/demo/index.html).
## Usage
### Installation
```
npm install --save @polymer/iron-validatable-behavior
```
### In a Polymer 3 element
```js
import {PolymerElement, html} from '@polymer/polymer';
import {mixinBehaviors} from '@polymer/polymer/lib/legacy/class.js';
import {IronValidatableBehavior} from '@polymer/iron-validatable-behavior/iron-validatable-behavior.js';
class SampleElement extends mixinBehaviors([IronValidatableBehavior], PolymerElement) {
static get template() {
return html`
`;
// Override this method if you want to implement custom validity
// for your element. This element is only valid if the value in the
// input is "cat".
function _getValidity() {
return this.$.input.value === 'cat';
}
}
}
customElements.define('sample-element', SampleElement);
```
### In an html file using the element
```html
```
## 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-validatable-behavior
cd iron-validatable-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
```