How to use global css styles in shadow dom

Question

Shadow dom encapsulate css styles, selectors don\'t cross the shadow boundary.

Question: How to use global common css styles in shadow

Answer 1

Non of the provided links work for me in Chrome 66 (as of 2018) so I ended up with this to customize custom element from outside:

  


class Element extends HTMLElement {
    constructor() {
        super();
        var shadow = this.attachShadow({mode: 'open'});

        var user_style = shadow.host.innerHTML.match(/