exec-funcdel.js

// Description:
// Given a function fn, an array of arguments args, and a timeout t in milliseconds, return a cancel function cancelFn.
// After a delay of t, fn should be called with args passed as parameters unless cancelFn was invoked before the delay of t milliseconds elapses, specifically at cancelT ms. In that case, fn should never be called.

// Example 1:
// Input: fn = (x) => x * 5, args = [2], t = 20, cancelT = 50
// Output: [{"time": 20, "returned": 10}]
// Explanation:
// const cancel = cancellable((x) => x * 5, [2], 20); // fn(2) called at t=20ms
// setTimeout(cancel, 50);
// The cancellation was scheduled to occur after a delay of cancelT (50ms), which happened after the execution of fn(2) at 20ms.

// Example 2:
// Input: fn = (x) => x**2, args = [2], t = 100, cancelT = 50
// Output: []
// Explanation:
// const cancel = cancellable((x) => x**2, [2], 100); // fn(2) not called
// setTimeout(cancel, 50);
// The cancellation was scheduled to occur after a delay of cancelT (50ms), which happened before the execution of fn(2) at 100ms, resulting in fn(2) never being called.

// Example 3:
// Input: fn = (x1, x2) => x1 * x2, args = [2,4], t = 30, cancelT = 100
// Output: [{"time": 30, "returned": 8}]
// Explanation:
// const cancel = cancellable((x1, x2) => x1 * x2, [2,4], 30); // fn(2,4) called at t=30ms
// setTimeout(cancel, 100);
// The cancellation was scheduled to occur after a delay of cancelT (100ms), which happened after the execution of fn(2,4) at 30ms.

// Constraints:
// fn is a function
// args is a valid JSON array
// 1 <= args.length <= 10
// 20 <= t <= 1000
// 10 <= cancelT <= 1000

var cancellable = function (fn, args, t) {
  const timeoutId = setTimeout(() => {
    fn(...args);
  }, t);

  function cancelFn() {
    clearTimeout(timeoutId);
  }

  return cancelFn;
};