Coordinates the flow of resizeable elements

Usage no npm install needed!

<script type="module">
  import polymerIronResizableBehavior from 'https://cdn.skypack.dev/@polymer/iron-resizable-behavior';


Published on NPM Build status Published on webcomponents.org


IronResizableBehavior is a behavior that can be used in Polymer elements to coordinate the flow of resize events between "resizers" (elements that control the size or hidden state of their children) and "resizables" (elements that need to be notified when they are resized or un-hidden by their parents in order to take action on their new measurements).

Elements that perform measurement should add the IronResizableBehavior behavior to their element definition and listen for the iron-resize event on themselves. This event will be fired when they become showing after having been hidden, when they are resized explicitly by another resizable, or when the window has been resized.

Note, the iron-resize event is non-bubbling.

See: Documentation, Demo.



npm install --save @polymer/iron-resizable-behavior

In a Polymer 3 element

import {PolymerElement, html} from '@polymer/polymer';
import {mixinBehaviors} from '@polymer/polymer/lib/legacy/class.js';
import {IronResizableBehavior} from '@polymer/iron-resizable-behavior/iron-resizable-behavior.js';

class SampleElement extends mixinBehaviors([IronResizableBehavior], PolymerElement) {
  static get template() {
    return html`
        :host {
          display: block;
          position: absolute;
          top: 0;
          right: 0;
          bottom: 0;
          left: 0;
      <span>width: [[width]] </span>
      <span>height: [[height]]</span>

  static get properties() {
    return {
      width: Number,
      height: Number,

  connectedCallback() {
    this.addEventListener('iron-resize', this.onIronResize.bind(this));

  onIronResize() {
    this.width = this.offsetWidth;
    this.height = this.offsetHeight;
customElements.define('sample-element', SampleElement);


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-resizable-behavior
cd iron-resizable-behavior
npm install
npm install -g polymer-cli

Running the demo locally

polymer serve --npm

Running the tests

polymer test --npm