radicalsInKanjifunction

The radicals a character is written with, fewest strokes first.

RADKFILE is stored radical by radical, each with the kanji that hold it, because that is the direction a search runs. A kanji page asks the opposite question, and a membership test per radical answers it, which is nothing next to keeping a second copy of the index the other way round. Simplest parts first, so the list reads the way the character is built up. Code point order breaks a tie, never a locale's collation, so the same character lists its parts in the same order on every machine.

import { radicalsInKanji } from "@johnmorrisdotca/bushu";

function radicalsInKanji(radicals: readonly Radical[], kanji: string): Radical[]

import { RADKFILE } from "@johnmorrisdotca/bushu/radkfile";
import { radicalsInKanji } from "@johnmorrisdotca/bushu";

const radicals = RADKFILE.radicals;
console.log(radicalsInKanji(radicals,"海").map(part=>part.radical));

[ '乞', '汁', '毋', '母' ]