onlyThatTime.ts

/*
 * 指定count回目の呼び出しでcallbackを叩く関数
*/
export function onlyThatTime(n: number, callback: () => any): () => void;
export function onlyThatTime<A>(n: number, callback: (a: A) => any, init?: [A]): (a: A) => void;
export function onlyThatTime<A1, A2>(n: number, callback: (a1: A1, a2: A2) => any, init?: [A1, A2]): (a1: A1, a2: A2) => void;
export function onlyThatTime<A1, A2, A3>(n: number, callback: (a1: A1, a2: A2, a3: A3) => any, init?: [A1, A2, A3]): (a1: A1, a2: A2, a3: A3) => void;
export function onlyThatTime(n: number, callback: Function, init: any[] = []): Function {
    let called = false;
    let count = 0;
    return (n <= 0) ? constant(awaiter)(callback.apply(null, init)) : awaiter;

    function awaiter() {
        count = count + 1;
        if (called) return;
        if (n === count) {
            called = true;
            callback.apply(null, arguments);
        }
    }
}

export function constant<T>(v: T) {
    return (..._x: any[]) => v;
}