BangleApps/apps/hebrew_calendar/app.js

const dayInMS = 86400000;

const DateProvider = { now: () => Date.now() };

const Layout = require("Layout");
const Locale = require("locale");

let nextEndingEvent;

function getCurrentEvents() {
  const now = DateProvider.now();

  const current = hebrewCalendar.filter(
    (x) => x.startEvent <= now && x.endEvent >= now
  );

  nextEndingEvent = current.reduce((acc, ev) => {
    return Math.min(acc, ev.endEvent);
  }, Infinity);

  return current.map((event, i) => {
    return {
      type: "txt",
      font: "12x20",
      id: "currentEvents" + i,
      label: event.desc,
      pad: 2,
      bgCol: g.theme.bg,
    };
  });
}

function getUpcomingEvents() {
  const now = DateProvider.now();

  const futureEvents = hebrewCalendar.filter(
    (x) => x.startEvent >= now && x.startEvent <= now + dayInMS
  );

  let warning;
  let eventsLeft = hebrewCalendar.filter(
    (x) => x.startEvent >= now && x.startEvent <= now + dayInMS * 14
  ).length;

  if (eventsLeft < 14) {
    warning = {
      startEvent: 0,
      type: "txt",
      font: "4x6",
      id: "warning",
      label: "only " + eventsLeft + " events left in calendar; update soon",
      pad: 2,
      bgCol: g.theme.bg,
    };
  }

  return futureEvents
    .slice(0, 2)
    .map((event, i) => {
      return {
        startEvent: event.startEvent,
        type: "txt",
        font: "6x8",
        id: "upcomingEvents" + 1,
        label: event.desc + " at " + Locale.time(new Date(event.startEvent), 1),
        pad: 2,
        bgCol: g.theme.bg,
      };
    })
    .concat(warning)
    .sort(function (a, b) {
      return a.startEvent - b.startEvent;
    });
}

function dateTime() {
  return (
    Locale.dow(new Date(), 1) +
    " " +
    Locale.date(new Date(), 1) +
    " " +
    Locale.time(new Date(), 1)
  );
}

function makeLayout() {
  return new Layout(
    {
      type: "v",
      c: [
        {
          type: "txt",
          font: "6x8",
          id: "title",
          label: "-- Hebrew Calendar Events --",
          pad: 2,
          bgCol: g.theme.bg2,
        },
        {
          type: "txt",
          font: "6x8",
          id: "currently",
          label: "Currently",
          pad: 2,
          bgCol: g.theme.bgH,
        },
      ]
        .concat(getCurrentEvents())
        .concat([
          {
            type: "txt",
            font: "6x8",
            label: "Upcoming",
            id: "upcoming",
            pad: 2,
            bgCol: g.theme.bgH,
          },
        ])
        .concat(getUpcomingEvents())
        .concat([
          {
            type: "txt",
            font: "Vector14",
            id: "time",
            label: dateTime(),
            pad: 2,
            bgCol: undefined,
          },
        ]),
    },
    { lazy: true }
  );
}
let layout = makeLayout();
// see also https://www.espruino.com/Bangle.js+Layout#updating-the-screen

// timeout used to update every minute
let drawTimeout;

function draw() {
  layout.time.label = dateTime();
  layout.render();

  // schedule a draw for the next minute
  if (drawTimeout) clearTimeout(drawTimeout);
  drawTimeout = setTimeout(function () {
    drawTimeout = undefined;
    draw();
  }, 60000 - (DateProvider.now() % 60000));
  console.log("updated time");
}

// update time and draw
g.clear();
Bangle.loadWidgets();
Bangle.drawWidgets();
draw();

function findNextEvent() {
  return hebrewCalendar.find((ev) => {
    return ev.startEvent > DateProvider.now();
  });
}

function updateCalendar() {
  layout.clear();
  layout = makeLayout();
  layout.forgetLazyState();
  layout.render();

  let nextChange = Math.min(
    findNextEvent().startEvent - DateProvider.now() + 5000,
    nextEndingEvent - DateProvider.now() + 5000
  );
  setTimeout(updateCalendar, nextChange);
  console.log("updated events");
}

updateCalendar();

Bangle.setUI("clock");