formats.exposed/public/gif/gif.js

// @ts-check

import * as base64 from "../common/vendor/base64-js.js";

const main = () => {
  // TODO: We may want a better UI here.
  // TODO: Handle errors.
  const fileDataBase64 = window.sessionStorage.getItem("fileData");
  if (!fileDataBase64) {
    location.href = "..";
    return;
  }
  const bytes = base64.toByteArray(fileDataBase64);

  console.log(bytes);
};

main();