The part property of the Element interface represents the part identifier(s) of the element (i.e. set using the part attribute), returned as a DOMTokenList. These can be used to style parts of a shadow DOM, via the ::part pseudo-element.


let elementPartList = element.part


The following excerpt is from our shadow-part example. Here the part attribute is used to find the shadow parts, and the part property is then used to change the part identifiers of each tab so the correct styling is applied to the active tab when tabs are clicked.  

let tabs = [];
let children = this.shadowRoot.children;

for(let elem of children) {
  if(elem.getAttribute('part')) {

tabs.forEach((tab) => {
  tab.addEventListener('click', (e) => {
    tabs.forEach((tab) => {
      tab.part = 'tab';
    e.target.part = 'tab active';



Specification Status Comment
Shadow Parts
The definition of 'Element.part' in that specification.
Working Draft

Browser compatibility

BCD tables only load in the browser

See also