class FilesItem extends HTMLTableRowElement { constructor() { super(); } connectedCallback() { const col1 = this.getAttribute('text') || ''; const col2 = this.getAttribute('col2') || ''; console.log('col1: ' + col1) console.log('col2: ' + col2) this.innerHTML = ` ${col1} ${col2} `; } } customElements.define('files-item', FilesItem, { extends: 'tr' });