Singleton module

singleton_module.ts

let count: number | null = null;

function init(): void {
    count = 0;
}

function increment(): void {
    if (count) {
        count++;
    }
}

function decrement(): void {
    if (count) {
        count--;
    }
}

function getCount(): number {
    if (!count) {
        throw new Error("Count has not been defined!");
    }
    return count;
}

export { init, increment, decrement, getCount };