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2715. Timeout Cancellation 👎

Problem

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 result = []

const fn = (x) => x * 5

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, [2], 20);

const maxT = Math.max(t, 50)
          
setTimeout(cancel, cancelT)

setTimeout(() => {
     console.log(result) // [{"time":20,"returned":10}]
}, 65)

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: 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: 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