Convert meters to pixels when given a map zoom level and a latitude

meters-to-pixels.js

const EARTH_CIR_METERS = 40075016.686;

function toRadians(degrees) {
  return degrees * Math.PI / 180;
};

const metersToPixels = (meters, latitude, zoom) => {
  const metersPerPixel = EARTH_CIR_METERS / Math.pow(2, zoom + 8) * Math.cos(toRadians(latitude));
  return meters / metersPerPixel
}

// get a circle radius in pixels given the radius in meters, at zoom level 8 and latitude 40
const pixelRadius = metersToPixels(1000, 40, 8)