# 2637. Promise Time Limit

## Description

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

## Solutions

• type Fn = (...params: any[]) => Promise<any>;

function timeLimit(fn: Fn, t: number): Fn {
return async function (...args) {
return Promise.race([
fn(...args),
new Promise((_, reject) => setTimeout(() => reject('Time Limit Exceeded'), t)),
]);
};
}

/**
* const limited = timeLimit((t) => new Promise(res => setTimeout(res, t)), 100);
* limited(150).catch(console.log) // "Time Limit Exceeded" at t=100ms
*/