WebUtil.js

const parseURL = (url) => {
  const n = url.indexOf("://");
  if (n < 0) {
    return null;
  }
  const protocol = url.substring(0, n + 3);
  const n2 = url.indexOf(":", n + 3);
  const n3 = url.indexOf("/", n + 3);
  if (n3 < 0) {
    const port = n2 < 0 ? 80 : parseInt(url.substring(n2 + 1));
    const host = n2 < 0 ? url.substring(n + 3) : url.substring(n + 3, n2);
    const path = "/";
    const query = null;
    return { protocol, port, host, path, query };
  }
  const port = n2 < 0 ? 80 : parseInt(url.substring(n2 + 1, n3));
  const host = n2 < 0 ? url.substring(n + 3, n3) : url.substring(n + 3, n2);
  const n4 = url.indexOf("?", n3);
  const path = n4 < 0 ? url.substring(n3) : url.substring(n3, n4);
  const query = n4 < 0 ? null : url.substring(n4 + 1);

  if (protocol == "file://") {
    const regexp = /(?<scheme>.+):\/\/(?<basename>.+)\/(?<filename>.+)/;
    const dirname = url.match(regexp).groups.basename + "/";
    return { protocol, port, host, path, query, dirname };
  }
  return { protocol, port, host, path: decodeURI(path), query };
};

const getQueryParam = (query, name) => {
  // query = location.search
  name = name.replace(/[\[]/, "\\[").replace(/[\]]/, "\\]");
  const regex = new RegExp("[\\?&]" + name + "=([^&#]*)");
  const res = regex.exec("?" + query);
  return res ? decodeURIComponent(res[1].replace(/\+/g, " ")) : "";
};

const existsDirSync = (path) => { // for Deno
  try {
    Deno.readDirSync(path);
    return true;
  } catch (e) {
    return false;
  }
};

const fetchJSON = async (path) => {
  try {
    if (globalThis.Deno) {
      return JSON.parse(await Deno.readTextFile(path));
    } else {
      return await (await fetch(path)).json();
    }
  } catch (e) {
    return null;
  }
}

export { existsDirSync, getQueryParam, parseURL, fetchJSON };