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2715. Timeout Cancellation

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

Solutions

• TypeScript
• Javascript

• function cancellable(fn: Function, args: any[], t: number): Function {
      const timer = setTimeout(() => fn(...args), t);
      return () => {
          clearTimeout(timer);
      };
  }
  
  /**
   *  const result = []
   *
   *  const fn = (x) => x * 5
   *  const args = [2], t = 20, cancelT = 50
   *
   *  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);
   *
   *  const maxT = Math.max(t, cancelT)
   *
   *  setTimeout(() => {
   *     cancel()
   *  }, cancelT)
   *
   *  setTimeout(() => {
   *     console.log(result) // [{"time":20,"returned":10}]
   *  }, maxT + 15)
   */
  
  

• /**
   * @param {Function} fn
   * @param {Array} args
   * @param {number} t
   * @return {Function}
   */
  var cancellable = function (fn, args, t) {
      const timer = setTimeout(() => fn(...args), t);
      return () => {
          clearTimeout(timer);
      };
  };
  
  /**
   *  const result = []
   *
   *  const fn = (x) => x * 5
   *  const args = [2], t = 20, cancelT = 50
   *
   *  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);
   *
   *  const maxT = Math.max(t, cancelT)
   *
   *  setTimeout(() => {
   *     cancel()
   *  }, cancelT)
   *
   *  setTimeout(() => {
   *     console.log(result) // [{"time":20,"returned":10}]
   *  }, maxT + 15)
   */
  
  

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