Square grid (Mercator) for Turfjs

grid.js

// creates GeoJSON features (using Turfjs) for square grid cells in the Mercator projection

function grid(minX,minY,maxX,maxY,size){	// arguments are in projected mercator units; conversion functions below
  var x = minX,
      y = minY,
      cells = [],
      x0,
      y0,
      x1,
      y1;
  while ( x < maxX ){
    y = minY;
    x0 = rad2deg( x );
    x1 = rad2deg( x + size );
    while ( y < maxY ){
      y0 = rad2deg( mercator_invert_y( y ) );
      y1 = rad2deg( mercator_invert_y( y + size ) );
      cells[ cells.length ] = turf.polygon([[
        [x0,y0],
        [x0,y1],
        [x1,y1],
        [x1,y0]
      ]]);
      y += size;
    }
    x += size;
  }
  return turf.featurecollection( cells );
}
var halfpi = Math.PI/2,
    pi = Math.PI;

function mercator(lon, lat) {
  lon = deg2rad(lon);
  lat = deg2rad(lat);
  return [lon, Math.log(Math.tan(pi / 4 + lat / 2))];
}
function mercator_invert(x, y) {
  return [x, 2 * Math.atan(Math.exp(y)) - halfpi];
}
function mercator_invert_y(y) {
  return 2 * Math.atan(Math.exp(y)) - halfpi;
}
function deg2rad(angle){
  return angle * .017453292519943295;
}
function rad2deg(angle){
  return angle * 57.29577951308232
}