[30 Days of JS] Interval Cancellation / Promise Time Limit

/**
 * @param {Function} fn
 * @param {Array} args
 * @param {number} t
 * @return {Function}
 */
var cancellable = function(fn, args, t) {
  fn(...args);

  const intervalId = setInterval(() => {
    fn(...args);
  }, t);

  return () => clearInterval(intervalId);
};

/**
 *  const result = [];
 *
 *  const fn = (x) => x * 2;
 *  const args = [4], t = 35, cancelTimeMs = 190;
 *
 *  const start = performance.now();
 *
 *  const log = (...argsArr) => {
 *      const diff = Math.floor(performance.now() - start);
 *      result.push({"time": diff, "returned": fn(...argsArr)});
 *  }
 *       
 *  const cancel = cancellable(log, args, t);
 *
 *  setTimeout(cancel, cancelTimeMs);
 *   
 *  setTimeout(() => {
 *      console.log(result); // [
 *                           //     {"time":0,"returned":8},
 *                           //     {"time":35,"returned":8},
 *                           //     {"time":70,"returned":8},
 *                           //     {"time":105,"returned":8},
 *                           //     {"time":140,"returned":8},
 *                           //     {"time":175,"returned":8}
 *                           // ]
 *  }, cancelTimeMs + t + 15)    
 */

• fn 바로 실행 후
• Interval 함수를 통해 지정된 시간까지 Interval 동작 수행 후 Clear

/**
 * @param {Function} fn
 * @param {number} t
 * @return {Function}
 */
var timeLimit = function(fn, t) {
    
    return async function(...args) {
        // Create a timeout promise that rejects after t milliseconds
        const timeoutPromise = new Promise((_, reject) => {
        setTimeout(() => {
            reject("Time Limit Exceeded");
            }, t);
        });

        // Race the original function and the timeout
        return Promise.race([
            fn(...args),   // Original async function
            timeoutPromise // Timeout rejection
        ]);
    }
};

/**
 * const limited = timeLimit((t) => new Promise(res => setTimeout(res, t)), 100);
 * limited(150).catch(console.log) // "Time Limit Exceeded" at t=100ms
 */

• reject를 사용해야 한다
• promise 만들어둔 뒤
• 입력받은 함수와 timeoutPromise를 하나의 Promise로 만들어주는 Promise.race를 통해 반환

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/race