Josh's Brain

Temporal is the new Date and Time API for Javascript.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Temporal

• Instant: a single instant in time. ex: unix timestamp.

• Duration: a length of time, such as two hours, or the difference between two timestamps.

• PlainTime: a time of day without a date. ex: 4:30 am.

• PlainDate: a date without a time: ex: June 12, 2026

• PlainDateTime: a date and time together, but no timezone.

• ZonedDateTime: a date and time together in a specific timezone.

Create a new Instant for right now.

// simple 'now'
const now = Temporal.Now.instant();
// now with local time zone
const nowInLocalZone = Temporal.Now.zonedDateTimeISO();
// now with specific time zone
const nowInPacific = Temporal.Now.zonedDateTimeISO("America/Los_Angeles");

Difference between two Instants

const a = Temporal.Instant.from("2026-05-26T12:00:00Z");
const b = Temporal.Instant.from("2026-05-26T15:30:00Z");
const diff = a.until(b, {
  largestUnit: "hours",
  smallestUnit: "minutes"
});
console.log(diff.toString());
// "PT3H30M"
console.log(diff.hours);   // 3
console.log(diff.minutes); // 30

Difference between two PlainDates (days without time)

const start = Temporal.PlainDate.from("2026-05-01");
const end = Temporal.PlainDate.from("2026-05-26");
const diff = start.until(end);
console.log(diff.toString());
// "P25D"
console.log(diff.days);
// 25

Convert Date to Instant

// Date from String
const date = new Date("2026-05-26T12:30:00Z"); 
// Date -> Temporal.Instant
const instant = Temporal.Instant.fromEpochMilliseconds(date.getTime());
// Temporal.Instant from a string
const instantLit = Temporal.Instant.from("2026-05-26T12:30:00Z");
// Temporal.Instant -> Date
const date = new Date(instant.epochMilliseconds);

To JSON

Converting a temporal object to JSON will turn it into a plain string. ex:

const obj = {
  createdAt: Temporal.Instant.from("2026-05-26T12:30:00Z"),
  dueDate: Temporal.PlainDate.from("2026-06-01"),
  meetingTime: Temporal.PlainDateTime.from("2026-06-01T09:30:00"),
  localMeeting: Temporal.ZonedDateTime.from(
    "2026-06-01T09:30:00[America/Los_Angeles]"
  )
};

console.log(JSON.stringify(obj, null, 2));

Produces:

{
  "createdAt": "2026-05-26T12:30:00Z",
  "dueDate": "2026-06-01",
  "meetingTime": "2026-06-01T09:30:00",
  "localMeeting": "2026-06-01T09:30:00-07:00[America/Los_Angeles]"
}

From JSON

To parse JSON and get the temporal object back you'll need to preserve the type and use a custom parser.

const obj = {
  createdAt: {
    type: "Temporal.Instant",
    value: Temporal.Now.instant().toString()
  }
};

const parsed = JSON.parse(json, (key, value) => {
  if (
    value &&
    value.type === "Temporal.Instant" &&
    typeof value.value === "string"
  ) {
    return Temporal.Instant.from(value.value);
  }
  return value;
});

asd

The create-react-app tool is deprecated. For a similar experience I use Vite.

Build a new react + typescript project with create and follow the prompts.

npm create vite@latest react-ts my-app-name -- --template react-ts

Get callbacks when the browser goes on or offline:

const hand_online = () => {
    console.log('we are online')
}
const hand_offline = () => {
    console.log('we are offline')
}
window.addEventListener("online", hand_online)
window.addEventListener("offline", hand_offline)

npx lets you create a command line tool that can be run without already having it installed. To turn your npm module into such a command give it should have a javascript file with a shebang line like this: #!/usr/bin/env node. This can be in your Typescript file and the compiler should make sure it ends up in the final output js file.

Then in your package.json file needs a bin entry pointing to the script like this:

{
  "bin": {
    "amx": "build/cli.js"
  }
}

Now publish your module and run it from another shell with npx -g modulename

You can run an npm script from a different directory by using the --prefix parameter

npm --prefix <path> run <command>

When you have just released a new package version and npm install in another project says the package doesn’t exist, that could be because it tried to fetch the package before it was really live on npmjs.org. The problem is that it then remembers this forever. So you need to clear out the cache with

npm cache clean --force