Quickstart: JavaScript

By the end of this page you will have a JavaScript program for Node.js that works out when a support ticket is due, counting only working hours, and how much of its SLA has been used.

InstallCopy Anchor Link

workclock needs Node.js 22 or later. In your project's directory:

npm i workclock

The package ships its TypeScript types. In a browser, load it through a bundler, or without one from workclock/web (Install: Browsers without a bundler).

Write the programCopy Anchor Link

A support desk in London works 09:00–17:00 on weekdays with a lunch hour, and is closed on 25 and 28 December 2026. A ticket opened at 16:30 on Christmas Eve with an 8-hour SLA is due at 09:30 on 30 December. At 11:00 on 29 December, 2 hours 30 minutes of the SLA have been used.

In JavaScript, save this as sla.mjs. Instants are Dates or ISO 8601 strings with an offset, and durations are milliseconds. London time is UTC in December, so 16:30 London time is "2026-12-24T16:30:00Z".

import { Schedule } from "workclock";

const HOUR = 3_600_000; // milliseconds

const support = new Schedule({
  timeZone: "Europe/London",
  rules: [
    { type: "workday", start: "09:00", end: "17:00" },
    { type: "break", start: "12:00", end: "13:00" },
    { type: "holidays", dates: ["2026-12-25", "2026-12-28"] },
  ],
});

const opened = "2026-12-24T16:30:00Z";
const due = support.add(opened, 8 * HOUR); // Date 2026-12-30T09:30:00.000Z
const now = "2026-12-29T11:00:00Z";
const used = support.between(opened, now); // 9000000 ms

console.log(`due ${due.toISOString()}, used ${used / HOUR} h`);

Run itCopy Anchor Link

node sla.mjs

It prints:

due 2026-12-30T09:30:00.000Z, used 2.5 h

09:30 UTC is 09:30 London time in December:

What just happenedCopy Anchor Link

new Schedule combined three rules, read in the Europe/London time zone: a "workday" rule for 09:00–17:00, which defaults to Monday to Friday, a "break" rule for 12:00–13:00, and a "holidays" rule for 25 and 28 December. support.add counted 8 hours of working time from the moment the ticket was opened, skipping the evening, the weekend, the holidays and the lunch hour, and returned the due instant as a Date. support.between returned the working time between two instants as a number of milliseconds, 9,000,000 here. js/examples/sla.mjs extends this program with nextPeriod, which finds when the current stretch of working time ends, and addMany, which computes many due times in one call.

Next stepsCopy Anchor Link

• Schedules: how rules combine into working time.
• Adding time: what add and sub return, including at the edges of working time.