[](https://www.npmjs.com/package/@polymer/iron-validator-behavior)
[](https://travis-ci.org/PolymerElements/iron-validator-behavior)
[](https://webcomponents.org/element/@polymer/iron-validator-behavior)
## IronValidatorBehavior
Use `IronValidatorBehavior` to implement a custom input/form validator. Element
instances implementing this behavior will be registered for use in elements that implement
`IronValidatableBehavior`.
See: [Documentation](https://www.webcomponents.org/element/@polymer/iron-validator-behavior),
[Demo](https://www.webcomponents.org/element/@polymer/iron-validator-behavior/demo/demo/index.html).
## Usage
### Installation
```
npm install --save @polymer/iron-validator-behavior
```
### In a Polymer 3 element that is a validator
```js
import {PolymerElement, html} from '@polymer/polymer';
import {mixinBehaviors} from '@polymer/polymer/lib/legacy/class.js';
import {IronValidatorBehavior} from '@polymer/iron-validator-behavior/iron-validator-behavior.js';
class SampleValidator extends mixinBehaviors([IronValidatorBehavior], PolymerElement){
// This validator only validates strings, and is only valid if
// the value is "cat".
function validate(value) {
return value === 'cat';
}
}
customElements.define('sample-validator', SampleValidator);
```
### Using this validator element in an html file
```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-validator-behavior
cd iron-validator-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
```