This is my modification of creating grids using D3 taken from Chuck Grimmet's block.
The idea is to create a grid of nrow-by-ncol rectangular grid drawn on a SVG element. I simplified the code by removing a for-loop block.
Modified http://d3js.org/d3.v4.min.js to a secure url
https://d3js.org/d3.v4.min.js