addToCalendar.txt

// script inspired by Intel, https://github.com/intelc/pathatpenncal/blob/main/script.js
// https://stackoverflow.com/questions/3665115/how-to-create-a-file-in-memory-for-user-to-download-but-not-through-server
function download(filename, text) {
    let element = document.createElement('a');
    element.setAttribute('href', 'data:text/plain;charset=utf-8,' + encodeURIComponent(text));
    element.setAttribute('download', filename);
    element.style.display = 'none';
    document.body.appendChild(element);
    element.click();
    document.body.removeChild(element);
  }

// https://ical.marudot.com/
const prefix =
`BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//ical.marudot.com//iCal Event Maker
CALSCALE:GREGORIAN
BEGIN:VTIMEZONE
TZID:America/Los_Angeles
LAST-MODIFIED:20201011T015911Z
TZURL:http://tzurl.org/zoneinfo-outlook/America/Los_Angeles
X-LIC-LOCATION:America/Los_Angeles
BEGIN:DAYLIGHT
TZNAME:PDT
TZOFFSETFROM:-0800
TZOFFSETTO:-0700
DTSTART:19700308T020000
RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=2SU
END:DAYLIGHT
BEGIN:STANDARD
TZNAME:PST
TZOFFSETFROM:-0700
TZOFFSETTO:-0800
DTSTART:19701101T020000
RRULE:FREQ=YEARLY;BYMONTH=11;BYDAY=1SU
END:STANDARD
END:VTIMEZONE\n`;

const suffix = 'END:VCALENDAR';

// https://bobbyhadz.com/blog/javascript-get-current-date-and-time-in-utc
const isoStr = new Date().toISOString().replaceAll("-", "").replaceAll(":", "").replaceAll(".", "");
const currentUTC = isoStr.slice(0, isoStr.length - 4) + "Z";

// https://github.com/30-seconds/30-seconds-of-code/blob/master/snippets/UUIDGeneratorBrowser.md
const UUIDGeneratorBrowser = () =>
  ([1e7] + -1e3 + -4e3 + -8e3 + -1e11).replace(/[018]/g, c =>
    (c ^ (crypto.getRandomValues(new Uint8Array(1))[0] & (15 >> (c / 4)))).toString(16)
  );

// convert collegeScheduler time format to UTC (substring) format
function timeConversion(clean_input) {
  if (String(clean_input).includes("pm")) {
      let clean_input_list = clean_input.replaceAll("pm", "").split(":");
      if (clean_input_list[0] == 12) {
        clean_input = String(Number(clean_input_list[0])) + clean_input_list[1];
      } else {
        clean_input = String(Number(clean_input_list[0]) + 12) + clean_input_list[1];
      }
  } else {
      let clean_input_list = clean_input.replaceAll("am", "").split(":");
      if (Number(clean_input_list[0])<10){
        clean_input = String("0" + clean_input_list[0] + clean_input_list[1]);
      } else {
        clean_input = String(clean_input_list[0] + clean_input_list[1]);
      }
  }
  return clean_input;
}

// initial date designation.
function getInitDate(input) {
  if (input === "M") {
    return "0829";
  } else if (input === "T") {
    return "0830";
  } else if (input === "W") {
    return "0831";
  } else if (input === "Th") {
    return "0901";
  } else if (input === "F") {
    return "0902";
  }
}

// setting up the file content
let cal_str = prefix;
let event_str = "";

// scrape data from the collegescheduler page
const a = document.querySelectorAll('body > section > div > main > div > div > div > div > table > thead > tr > th')[3].textContent;
const b = Array.from(document.querySelectorAll('body > section > div > main > div > div > div > div > table > tbody'));

for (let i = 0; i < b.length; i++) {
  const c = b[i].childNodes[0].querySelectorAll('td');
  let subject, course, daysAndLocations;

  // separate enrolled classes from shopping cart
  if (a === 'Status') {
    subject = c[5].textContent;
    course = c[6].textContent;
    daysAndLocations = c[11].textContent.split(' ');
  } else {
    subject = c[4].textContent;
    course = c[5].textContent;
    daysAndLocations = c[10].textContent.split(' ');
  }

  let classLocation = '';
  for (let j = 5; j < daysAndLocations.length; j++) {
    classLocation = classLocation + ' ' + daysAndLocations[j];
  }
  classLocation = classLocation.slice(1);

  let days = [];
  while (daysAndLocations[0]) {
    const fc = daysAndLocations[0][0];
    const sc = daysAndLocations[0][1];
    if (fc === 'T' && sc === 'h') {
      days.push("Th");
      daysAndLocations[0] = daysAndLocations[0].slice(2);
    } else {
      days.push(fc);
      daysAndLocations[0] = daysAndLocations[0].slice(1);
    }
  }

  // write class into event
  while (days.length > 0) {
    const day = days.shift();
    event_str =
`BEGIN:VEVENT
DTSTAMP:${currentUTC}
UID:${UUIDGeneratorBrowser()}
DTSTART;TZID=America/Los_Angeles:2022${getInitDate(day)}T${timeConversion(daysAndLocations[1])}00
RRULE:FREQ=DAILY;INTERVAL=7;COUNT=16
DTEND;TZID=America/Los_Angeles:2022${getInitDate(day)}T${timeConversion(daysAndLocations[3])}00
SUMMARY:${subject + ' - ' + course}
LOCATION:${classLocation}
END:VEVENT\n`;
    cal_str = cal_str + event_str;
  }
}

// finish the content with some suffix
cal_str = cal_str + suffix;

// start file download
download("course_calendar.ics", cal_str);