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Here you can Sed posuere consectetur est at lobortis. Donec ullamcorper nulla non metus auctor fringilla. Maecenas sed diam eget risus varius blandit sit amet non magna. Donec id elit non mi porta gravida at eget metus. Praesent commodo cursus magna, vel scelerisque nisl consectetur et.

              <!-- define element -->
<dom-module id="custom-element">
  <!-- initialize element -->

<!-- add element to page -->
<custom-element title="ES6 Polymer Behaviors - Extending Multiple Behaviors"></custom-element>
              'use strict';

(() => {
  // define a behavior
  const FirstBehavior = {
    properties: {
      first: {
        type: String,
        value: 'First Behavior'
  // define another behavior
  const SecondBehavior = {
    properties: {
      second: {
        type: String,
        value: 'Second Behavior'
  // define another behavior
  const ThirdBehavior = {
    properties: {
      third: {
        type: String,
        value: 'Third Behavior'
  // define a behavior which bundles the related behaviors ...
  const FourthBehavior = [
  // add the behavior to a namespace ...
  const ns = (window.SomeNamespace = window.SomeNamespace || {
    'FirstBehavior'  : FirstBehavior,
    'SecondBehavior' : SecondBehavior,
    'ThirdBehavior'  : ThirdBehavior,
    'FourthBehavior' : FourthBehavior

// define element class ...
class CustomElement {
    this.is = 'custom-element';
    this.properties = {
      title: {
        type: String
  // implement behaviors getter, returning an array of behaviors which are to be 
  // extended via this._behaviors, or, assigning and returning the array of behaviors 
  // to be extended should this._behaviors be undefined ...
  get behaviors() {
    const ns = window.SomeNamespace || {};
    return this._behaviors || (this._behaviors = [
  // implement corresponding setter ...
  set behaviors(val) {
    this._behaviors = val;
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