fonteva-design-guide/force-app/main/default/lwc/pfmButtonGroup/pfmButtonGroup.js

## Dev, Build and Test

import { LightningElement, track, api } from 'lwc';

export default class PfmButtonGroup extends LightningElement {
    @api backend;

    renderedCallback() {
        let btn = this.querySelectorAll('c-pfm-button-group c-pfm-button');
        let self = this;

        btn.forEach(function (i) {
            i.classList.add('pfm-button_grouped');
            if (self.backend) {
                i.classList.add('pfm-button_backend');
            }
        });
    }
}