Synchronously read a svelte 3/4 store / Readable

svelte-read.ts

import type { Readable } from "svelte/store";

const UNSET = Symbol();
export function read<T>(store: Readable<T>): T {
  let value: T | typeof UNSET = UNSET;
  store.subscribe((v) => (value = v))();
  if (UNSET === value) {
    throw new Error("Readable did not react synchronously");
  }
  return value;
}