https://westerncape.gov.za/modules/rogerwilco/rw_grid/modules/rw_grid_libraries/js/rw-grid.js?tku0w2

1/*=================================*/
2/* WYSIWYG CTA - JS file */
3/*=================================*/
4
5var grids = document.querySelectorAll('.rw-grid'),
6    gridsArr = [],
7    gridIdx;
8
9for (gridIdx = 0; gridIdx < grids.length; gridIdx++) {
10    gridsArr.push(grids[gridIdx]);
11}
12
13var rowVal,
14    gridRow;
15gridsArr.forEach(function(grid) {
16    rowVal = grid.attributes.items.value;
17    gridRow = grid.querySelector('.rw-grid--row');
18    gridRow.style.cssText = 'grid-template-columns: repeat(' + rowVal + ', 1fr);';
19});