@smartput/tempo

Beats per minute, and its bridge to duration.

Canonical in beats per minute — two units, the second-smallest table in the repo.

Three doors, one table. The kind descriptor is for the engine, /validate is free functions over JS numbers, /class is an immutable value class — and all three read the same UnitTable, so a unit added once is added everywhere. See Validating without the engine.

Setup

npm add @smartput/tempo

Example

import { parseTempo, asTempo, formatTempo } from "@smartput/tempo/validate";
import { Tempo } from "@smartput/tempo/class";

parseTempo("120 bpm")                       // {"ok":true,"value":120,"unit":"bpm","raw":"120"}
asTempo("120 bpm", "hz")                    // {"ok":true,"value":2,"unit":"hz","raw":"2"}
formatTempo(parseTempo("120 bpm"))          // "120bpm"
String(Tempo.parse("120 bpm"))              // "120bpm"

// …and the same table through the engine:
engine.evaluate("120 bpm in hz").formatted  // "2 hertz"
engine.evaluate("2 hz in bpm").formatted    // "120 bpm"

parse and as never throw — they answer { ok: true, … } or { ok: false, code, input }. The value class throws on bad input and Tempo.tryParse does not. All three read the one UnitTable below.

Entry points

| Import | Contents | | --- | --- | | @smartput/tempo | The package root. | | @smartput/tempo/units | The UnitTable: ratios and aliases, with no engine and no Decimal. | | @smartput/tempo/validate | Free functions over JS numbers. Ok \| Err, never a throw. | | @smartput/tempo/class | The immutable value class. | | @smartput/tempo/locale/<id> | One language's words for this kind. 17 ship: en, de, fr, es, pt, it, nl, zh, ja, ar, ru, pl, tr, hi, ko, id, uk. |

Units

Read from the table itself, not typed out — a unit added to the source appears here on the next bun run docs:packages. Ratios are decimal strings, which is what lets the engine widen them to Decimal without a float in between.

TEMPO_UNITS

| Unit | Ratio to bpm | Aliases | | --- | --- | --- | | bpm | 1 | bpm | | hz | 60 | hz hertz |

Runtime exports

Type-only exports are erased and do not appear here.

TEMPO_UNITS · tempo

Dependencies

• @smartput/kind
• @smartput/shared

What it costs

Ceilings, not measurements. bun run check-size bundles each entry with bun build --minify and fails if a row crosses its ceiling or drops more than 30 % below it — a budget that is only an upper bound reports a vanished graph as a triumph.

| Import | Minified | Gzipped | | --- | --- | --- | | tempo/validate parseTempo only | ≤ 1.1 kB | ≤ 650 B | | tempo/class | ≤ 4.5 kB | ≤ 1.8 kB |

Generated by scripts/gen-readmes.ts — run bun run docs:readmes. Every output above was produced by running the line beside it. The full page, with live demos, is docs/packages/tempo.md.