Go's time.ParseDuration in TypeScript

✓ Verified: Go 1.23

How to use

Install via yarn add locutus and import: import { ParseDuration } from 'locutus/golang/time/ParseDuration'.

Or with CommonJS: const { ParseDuration } = require('locutus/golang/time/ParseDuration')

Use a bundler that supports tree-shaking so you only ship the functions you actually use. Vite, webpack, Rollup, and Parcel all handle this. For server-side use this is less of a concern.

Examples

These examples are extracted from test cases that automatically verify our functions against their native counterparts.

#	code	expected result
1	`ParseDuration('300ms')`	`300`
2	`ParseDuration('1h2m3.5s')`	`3723500`
3	`ParseDuration('-1.5h')`	`-5400000`
4	`ParseDuration('2h45m')`	`9900000`

Notes

Parses Go duration strings and returns milliseconds.
Supports ns, us/µs, ms, s, m, h units and chained segments.

Here's what our current TypeScript equivalent to Go's time.ParseDuration looks like.

const DURATION_UNIT_TO_MS: Record<string, number> = {
  ns: 1e-6,
  us: 1e-3,
  '\u00b5s': 1e-3,
  ms: 1,
  s: 1_000,
  m: 60_000,
  h: 3_600_000,
}

const DURATION_PART_REGEX = /^(\d+(?:\.\d+)?|\.\d+)(ns|us|\u00b5s|ms|s|m|h)/

export function ParseDuration(s: string): number {
  //      discuss at: https://locutus.io/golang/time/ParseDuration
  // parity verified: Go 1.23
  //     original by: Kevin van Zonneveld (https://kvz.io)
  //          note 1: Parses Go duration strings and returns milliseconds.
  //          note 2: Supports ns, us/µs, ms, s, m, h units and chained segments.
  //       example 1: ParseDuration('300ms')
  //       returns 1: 300
  //       example 2: ParseDuration('1h2m3.5s')
  //       returns 2: 3723500
  //       example 3: ParseDuration('-1.5h')
  //       returns 3: -5400000
  //       example 4: ParseDuration('2h45m')
  //       returns 4: 9900000

  const raw = String(s).trim()
  if (raw === '') {
    throw new TypeError('ParseDuration(): invalid duration')
  }

  let sign = 1
  let rest = raw

  if (rest.startsWith('+') || rest.startsWith('-')) {
    sign = rest[0] === '-' ? -1 : 1
    rest = rest.slice(1)
  }

  if (rest === '0') {
    return 0
  }

  let totalMs = 0

  while (rest.length > 0) {
    const match = DURATION_PART_REGEX.exec(rest)
    if (!match) {
      throw new TypeError('ParseDuration(): invalid duration')
    }

    const valueLiteral = match[1]
    const unit = match[2]
    if (!valueLiteral || !unit) {
      throw new TypeError('ParseDuration(): invalid duration')
    }

    const value = Number.parseFloat(valueLiteral)
    const multiplier = DURATION_UNIT_TO_MS[unit]

    if (!Number.isFinite(value) || multiplier === undefined) {
      throw new TypeError('ParseDuration(): invalid duration')
    }

    totalMs += value * multiplier
    rest = rest.slice(match[0].length)
  }

  return sign * totalMs
}

Improve this function

Locutus is a community effort following The McDonald's Theory: we ship first iterations, hoping others will improve them. If you see something that could be better, we'd love your contribution.

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