Reference

Streams, draws and seeds

import { … } from "@johnmorrisdotca/tane";

9.8 kB minified and gzipped, with everything it imports (measured with esbuild)

Tane 種: seeded random numbers and daily seeds.

One seed, the same numbers everywhere: a small generator, the draws a game needs from it, seeds that travel in an address with ranges kept aside, one seed a day, and a stream's position written down and read back. No dependencies and no DOM; @johnmorrisdotca/tane/react adds two hooks, and tane is the same thing from a terminal.

Exports

Name	Kind	What it is
`addDays`	function	The day `by` days after (or, negative, before) a day.
`below`	function	An integer in [0, n): one draw.
`chance`	function	True with probability `p`, from 0 (never) to 1 (always): one draw.
`checkBlocks`	function	The blocks in ascending order, checked: whole numbers, inside 1 to `most`, none overlapping another.
`CLI_MAX_COUNT`	constant	The most numbers one run prints.
`cliLanguage`	function	The language the command line speaks: `--lang`, or the environment's, or the system's; Japanese for `ja…`, English for anything else.
`CliResult`	type	What the command line came to.
`CliSurroundings`	type	What the command line is run in.
`counted`	function	A seeded stream that counts its own draws, so that it can be written down at any moment and picked up later: `const random = counted(42)`, draw from it as from any stream, then keep `random.position()`.
`CountedRandom`	type	A stream that knows where it is: call it for the next number, as any `Random`; read `seed` and `draws`, or take its `position()`.
`CSV_COLUMNS`	constant	The columns of the CSV, in order.
`dailySeed`	function	Today's seed, the date as a number: 2026-09-30 is 20260930.
`dayKey`	function	The day a moment falls on, in UTC or in the named IANA time zone.
`DayKey`	type	A calendar date, `YYYY-MM-DD`.
`dayOfSeed`	function	The day a seed names inside a block, or null for a seed that names none.
`daysBetween`	function	How many days `to` is after `from`: negative when it is before.
`daySeed`	function	A day's seed inside a block kept for it: the block's first seed plus the date as a number.
`deriveSeed`	function	A seed of its own for one part of something seeded: `deriveSeed(game, "deck")` and `deriveSeed(game, "dice")` are two unrelated streams from one game's seed, and adding a third part later moves neither.
`distinctBelow`	function	`count` different integers below `limit`, in the order drawn, by drawing again whenever a number comes up twice.
`drawSeed`	function	A seed from 1 to `most`, any of them as likely as another, skipping every reserved block: one draw.
`DrawSeedOptions`	type	Where a drawn seed may land.
`fillIn`	function	Put values into a string's braces: `fillIn("Seed {seed}", { seed: 42 })` is "Seed 42".
`float`	function	A number in [min, max): one draw.
`fork`	function	A new, independent stream split off another: it takes one draw from `random` and seeds a fresh generator from it.
`freshSeed`	function	A new seed for something nobody asked for by number, drawn from `Math.random`.
`fromJSON`	function	A position from JSON that `toJSON` wrote.
`fromText`	function	A position from a line `toText` wrote, with any space around it.
`hashSeed`	function	A seed from any text: `hashSeed("room-7")` is the same unsigned 32-bit integer everywhere.
`inBlock`	function	Whether a seed falls inside a block.
`int`	function	An integer from `min` to `max`, both included: one draw.
`isDayKey`	function	Whether a text is a real date written `YYYY-MM-DD`: 2026-02-30 is not.
`isSeed`	function	Whether a value read from outside (an address, a request body) is a seed: an integer from 1 to `most`.
`Language`	type	The languages Tane speaks.
`languageOf`	function	The language a tag such as `ja-JP` or `en_US.UTF-8` names: Japanese for anything that starts `ja`, English otherwise.
`MAX_CSV_ROWS`	constant	The most rows `toCSV` writes at once.
`mulberry32`	function	A seeded stream: `mulberry32(42)` returns the same numbers every time it is made.
`nextDayStart`	function	The first moment of the day after the one `at` falls on, in that zone: when a daily seed next changes.
`normal`	function	A number from a normal distribution (Box–Muller): two draws.
`pick`	function	One item of a list, each as likely as the next: one draw.
`Random`	type	A number in [0, 1), like `Math.random`, from a stream a seed fixes.
`randomAt`	function	A stream that starts `draws` numbers into `seed`'s: `randomAt(42, 7)()` is the eighth number of `mulberry32(42)`, reached without drawing the first seven.
`runCli`	function	Run the command line.
`sample`	function	`count` items of a list, no item twice, in the order drawn: a partial Fisher–Yates, one draw each.
`SAVE_FORMAT`	constant	The shape of the JSON and the text this package writes.
`savedStream`	function	A position as the object `toJSON` writes: the format, the seed, the draws and the state they come to.
`SavedStream`	type	A stream's position as `toJSON` writes it.
`SEED_MOST`	constant	The largest seed: it travels as a plain integer, so it stays a positive 32-bit signed one.
`SeedBlock`	type	A range of seeds kept aside: `from` up to, not including, `from + size`.
`seededRandom`	function	A seeded stream.
`seedFrom`	function	A seed from whatever a person typed or a link carried.
`shuffle`	function	The list in place, in a random order (Fisher–Yates, from the end): one draw for each item but the first.
`shuffled`	function	A shuffled copy; the list given is left alone.
`stateAt`	function	The generator's state after `draws` numbers have been taken from `seed`: an unsigned 32-bit integer.
`step`	function	One step of mulberry32 as a pure function: the number drawn and the state to keep for the next one.
`Step`	type	One draw and the state after it, for code that keeps the state itself (in a database row, say).
`StreamPosition`	type	Where a stream is: the seed it started from, and how many numbers have been drawn from it.
`STRINGS`	constant	Every string, in both languages.
`TaneStrings`	type	The names of the strings.
`toCSV`	function	The next `count` numbers from a position as CSV for a spreadsheet: a header, then one row a draw, with the draw's number counted from 1, its value, and the generator's state after it.
`toJSON`	function	A position as JSON, two spaces deep, with the format's number first.
`toText`	function	A position as one line to paste into a chat or a bug report: `tane:1:42:7` is format 1, seed 42, 7 draws in.
`VERSION`	constant	The version of this package, as `package.json` has it.
`weightedIndex`	function	An index into `weights`, each chosen in proportion to its weight: one draw.
`weightedPick`	function	One item, chosen by the matching weight: one draw.

View source Edit on GitHubMade from the source of @johnmorrisdotca/tane 1.3.0.