2637. Promise Time Limit

Problem

Given an asynchronous function fn and a time t in milliseconds, return a new time limited version of the input function. fn takes arguments provided to the time limited function.

The time limited function should follow these rules:

• If the fn completes within the time limit of t milliseconds, the time limited function should resolve with the result.
• If the execution of the fn exceeds the time limit, the time limited function should reject with the string "Time Limit Exceeded".

Example 1:

Input:
fn = async (n) => {
  await new Promise(res => setTimeout(res, 100));
  return n * n;
}
inputs = [5]
t = 50
Output: {"rejected":"Time Limit Exceeded","time":50}
Explanation:
const limited = timeLimit(fn, t)
const start = performance.now()
let result;
try {
   const res = await limited(...inputs)
   result = {"resolved": res, "time": Math.floor(performance.now() - start)};
} catch (err) {
   result = {"rejected": err, "time": Math.floor(performance.now() - start)};
}
console.log(result) // Output

The provided function is set to resolve after 100ms. However, the time limit is set to 50ms. It rejects at t=50ms because the time limit was reached.

Example 2:

Input:
fn = async (n) => {
  await new Promise(res => setTimeout(res, 100));
  return n * n;
}
inputs = [5]
t = 150
Output: {"resolved":25,"time":100}
Explanation:
The function resolved 5 * 5 = 25 at t=100ms. The time limit is never reached.

Example 3:

Input:
fn = async (a, b) => {
  await new Promise(res => setTimeout(res, 120));
  return a + b;
}
inputs = [5,10]
t = 150
Output: {"resolved":15,"time":120}
Explanation:
​​​​The function resolved 5 + 10 = 15 at t=120ms. The time limit is never reached.

Example 4:

Input:
fn = async () => {
  throw "Error";
}
inputs = []
t = 1000
Output: {"rejected":"Error","time":0}
Explanation:
The function immediately throws an error.

Constraints:

• 0 <= inputs.length <= 10
• 0 <= t <= 1000
• fn returns a promise

Solution (Javascript)

/**
 * @param {Function} fn
 * @param {number} t
 * @return {Function}
 */
var timeLimit = function (fn, t) {
  return async function (...args) {
    const originalFnPromise = fn(...args);

    const timeoutPromise = new Promise((_, reject) => {
      setTimeout(() => {
        reject("Time Limit Exceeded");
      }, t);
    });

    return Promise.race([originalFnPromise, timeoutPromise]);
  };
};

Explain:

nope.

Complexity:

• Time complexity : O(n).
• Space complexity : O(n).