2715-execute-cancellable-function-with-delay.md

2715. Execute Cancellable Function With Delay

Easy

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Given a function fn, an array or 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 called first. In that case, fn should never be called.

 

Example 1:

Input: fn = (x) => x * 5, args = [2], t = 20
Output: [{"time": 20, "returned": 10}]
Explanation: 
const cancelTime = 50
const cancel = cancellable((x) => x * 5, [2], 20); // fn(2) called at t=20ms
setTimeout(cancel, cancelTime);

The cancellation was scheduled to occur after a delay of cancelTime (50ms), which happened after the execution of fn(2) at 20ms.

Example 2:

Input: fn = (x) => x**2, args = [2], t = 100
Output: []
Explanation: 
const cancelTime = 50 
const cancel = cancellable((x) => x**2, [2], 100); // fn(2) not called
setTimeout(cancel, cancelTime);

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

The cancellation was scheduled to occur after a delay of cancelTime (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