vaadin grid html api

app-vaadin-grid.js

app.js

customElements.whenDefined('vaadin-grid').then(_ => {

const grid = document.querySelector('vaadin-grid');
console.dir(grid);
grid.dataProvide = (params, callback) => {
  fetch('http://url').
then(response => response.json()).then (
json => callback(json, json.lenth));
}
});