class based css styling for polymer's shadow dom elements

class based css styling for polymer's shadow dom elements

By : George Corbu AG
Date : November 19 2020, 12:41 AM
will be helpful for those in need I am trying to add styles to my shadow DOM elements using JavaScript. I am aware that you can select each element via their id by using this.$.elementID, but are there methods to select the element via its class properties? , There is an option to access Shadow DOM directly using,
code :

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Styling native Shadow DOM elements

Styling native Shadow DOM elements

By : katazina
Date : March 29 2020, 07:55 AM
To fix this issue -webkit-appearance (or -moz-appearance) is thought to reset/update the browser-style for an element, e.g. to style a div like a button (see w3c reference, and this jsFiddle), or reset the style of a select (see this jsFiddle). If you browse with an apple mobile device for example, you will see buttons are rounded by default. -webkit-appearance:none; will prevent that. (see also here). It seems it is not fully implemented on desktop browsers, yet.
I was able to achieve the effect you desire with (jsFiddle):
code :
input[type=range]::-webkit-slider-thumb {
    -webkit-box-shadow: inset 0 0 10px 10px yellow;
input[type=range]::-webkit-slider-thumb {
-webkit-appearance: none;
outline:solid 1px yellow;  


/* we have to set that, because it's not inherited anymore */
width: 10px;
height: 20px;


input[type=range] {
    -webkit-appearance: none; /* this is important */

input[type=range]::-webkit-slider-runnable-track {
Styling elements based on parent

Styling elements based on parent

By : Sanjay Krishna
Date : March 29 2020, 07:55 AM
this one helps. Actually, if that class is unique to the table in question, nth-child is the way to go:
code :
.myTable tr:first-child td:nth-child(1), 
.myTable tr:first-child td:nth-child(2) {
  background-color: red;
.myTable td:nth-child(1), 
.myTable td:nth-child(2) {
  background-color: red;
Loading polymers iron-list in parts, when scrollbar is outside shadow-dom

Loading polymers iron-list in parts, when scrollbar is outside shadow-dom

By : Francis Michelraj
Date : March 29 2020, 07:55 AM
To fix the issue you can do I think you need to get a right scrollTarget cause your approach doesn't work correct. You need to find app-header element and get its own scrollTarget:
code :
ready: function(){
   //get parent node and query app-header
   this.$.ironList.scrollTarget = this.domHost.$$('app-header').scrollTarget;
Styling Shadow DOM elements using ::part

Styling Shadow DOM elements using ::part

By : user3398031
Date : March 29 2020, 07:55 AM
With these it helps The part attribute must be defined:
inside the Shadow DOM, on the element which you want to apply the style to.
code :
<p is="word-count">
    <span part="some-box">Words: 120</span>
[is=word-count]::part(some-box) {
  color: beige;
class WordCount extends HTMLParagraphElement {
  constructor() {
    // Always call super first in constructor

    // count words in element's parent element
    var wcParent = this.parentNode;

    function countWords(node) {
      var text = node.innerText || node.textContent
      return text.trim().split(/\s+/g).length;

    var count = 'Words: ' + countWords(wcParent);

    // Create a shadow root
    var shadow = this.attachShadow({
      mode: 'open'

    // Create text node and add word count to it
    var text = document.createElement('span');
    text.textContent = count;
    text.setAttribute( 'part', 'some-box' )

    // Append it to the shadow root

    // Update count when element content changes
    setInterval(function() {
      var count = 'Words: ' + countWords(wcParent);
      text.textContent = count;
    }, 200)

// Define the new element
customElements.define('word-count', WordCount, {
  extends: 'p'
p::part(some-box) {
   color: red ;
<h1>Word count rating widget</h1>

<article contenteditable="">
  <h2>Sample heading</h2>

  <p>Add some words please. 

  <p is="word-count">
Will Angular 2.0 understand Polymers shadow DOM?

Will Angular 2.0 understand Polymers shadow DOM?

By : Shihabudheen .K.H
Date : March 29 2020, 07:55 AM
hop of those help? The answer is actually yes, as per the answer of Miško Hevery at a ngEurope conference's Q&A a couple of days ago. And this makes sense in the context of Angular 2.0 embracing Web Components.
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