Extract Host and TLD from valid url

extract-host-tld.js

// Assumes a valid url
export function extractHostAndTLD(url) {
  const reDot = /\./g;
  const reAfterDot = /\.(.*)$/;
  const boxedUrl = new URL(url);
  const host = boxedUrl.host;

  if (host.match(reDot).length > 1) {
    // Ignore the inclusive match and only extract the captured group
    const [_, afterDot] = host.match(reAfterDot);
    return afterDot;
  }

  return host;
}

// Sample test
describe("extractHostAndTLD", () => {
  it("returns the correct string", () => {
    expect(extractHostAndTLD("https://hello.world.io/segment1")).toEqual(
      "world.io"
    );
    expect(extractHostAndTLD("https://world.io/segment1")).toEqual("world.io");
    expect(extractHostAndTLD("https://hello.world.io")).toEqual("world.io");
    expect(extractHostAndTLD("https://world.io")).toEqual("world.io");
  });
});