typescript 29 lines · 7 steps

Parsing ISO 8601 durations to seconds

A single regex plus a units-to-seconds table turns strings like PT1H30M into a numeric total.

Explained by highlit

Intermediate regex parsing iso-8601 validation lookup-table

1const ISO_DURATION = /^P(?:(\d+(?:\.\d+)?)Y)?(?:(\d+(?:\.\d+)?)M)?(?:(\d+(?:\.\d+)?)W)?(?:(\d+(?:\.\d+)?)D)?(?:T(?:(\d+(?:\.\d+)?)H)?(?:(\d+(?:\.\d+)?)M)?(?:(\d+(?:\.\d+)?)S)?)?$/;
2 
3const SECONDS_PER = {
4  years: 365 * 24 * 60 * 60,
5  months: 30 * 24 * 60 * 60,
6  weeks: 7 * 24 * 60 * 60,
7  days: 24 * 60 * 60,
8  hours: 60 * 60,
9  minutes: 60,
10  seconds: 1,
11} as const;
12 
13export function parseIsoDuration(input: string): number {
14  const match = ISO_DURATION.exec(input.trim());
15  if (!match || match[0] === "P" || match[0] === "PT") {
16    throw new RangeError(`Invalid ISO 8601 duration: ${input}`);
17  }
18 
19  const [, years, months, weeks, days, hours, minutes, seconds] = match;
20  const parts = { years, months, weeks, days, hours, minutes, seconds };
21 
22  let total = 0;
23  for (const [unit, raw] of Object.entries(parts)) {
24    if (raw === undefined) continue;
25    total += parseFloat(raw) * SECONDS_PER[unit as keyof typeof SECONDS_PER];
26  }
27 
28  return total;
29}

01 / 01

STEP 01

Walkthrough

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Three takeaways

1A well-structured regex with capture groups can both validate and extract fields in one pass.
2Pairing named units with a conversion table keeps the accumulation loop tiny and data-driven.
3Guarding against the empty P/PT matches closes a gap the regex alone would let through.

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