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, Demo.
npm install --save @polymer/iron-validatable-behavior
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`
<style>
:host {
border: 1px solid green;
color: green;
}
:host([invalid]) {
border: 1px solid red;
color: red;
}
</style>
<input id="input">
`;
// 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);<html>
<head>
<script type="module" src="./sample-element.js"></script>
</head>
<body>
<sample-element id="el"></sample-element>
<button onclick="el.validate()">Validate!</button>
</body>
</html>If you want to send a PR to this element, here are the instructions for running the tests and demo locally:
git clone https://github.com/PolymerElements/iron-validatable-behavior
cd iron-validatable-behavior
npm install
npm install -g polymer-clipolymer serve --npm
open http://127.0.0.1:<port>/demo/polymer test --npm