const hostEl = document.querySelector('#grid');

const grid = GridStack.init({
    column: 12,
    cellHeight: 'initial',
    float: false,
}, hostEl);

grid.addWidget({w: 2, h: 2, content: 'item 1'});

document.querySelector('#increase-width')
.addEventListener('click', function() {
  hostEl.style.width = '1000px';

  // doesn't work
  grid.cellHeight('initial');

  // but works with timeout
  setTimeout(()=>grid.cellHeight('initial'), 300);
});