proj4 to D3 projection

proj4toD3.js

function radiansToDegrees(radians) {
  return (radians * 180) / Math.PI;
}

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

function proj4toD3(proj4String) {
  const proj4 = require("proj4");
  const d3 = require("d3");
  const proj = proj4(proj4String);
  const project = function(lambda, phi) {
    return proj.forward([lambda, phi].map(radiansToDegrees));
  };
  project.invert = function(x, y) {
    return proj.inverse([x, y]).map(degreesToRadians);
  };
  const projection = d3.geoProjection(project);
  return projection;
};