sdekna

// REPL: https://svelte.dev/repl/2c56758fb2ca4de9bf842e3dfb61ed36

function customStore<T>(initialValue: T, mutationFunction: (value: T)=>T, validationFunction: (value: T)=>boolean) {

  let currentValue = initialValue
  let previousValue: T | null = null;

  const subscribers = new Set<(value: T, previousValue: T | null) => void>();

  const set = (value: T): void => {