Promise Time Limit in JavaScript
Given an asyncronous function fn and a time t in milliseconds, return a new time limited version of the input function.
A time limited function is a function that is identical to the original unless it takes longer than t milliseconds to fullfill. In that case, it will reject with "Time Limit Exceeded". Note that it should reject with a string, not an Error.
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:
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.
/**
* @param {Function} fn
* @param {number} t
* @return {Function}
*/
var timeLimit = function(fn, t) {
return async function(...args) {
return Promise.race([
fn.apply(this, args), // Execute the wrapped function
new Promise((_, reject) => setTimeout(() => reject("Time Limit Exceeded"), t)) // Timeout promise
]);
};
};
const limited = timeLimit((t) => new Promise((res) => setTimeout(res, t)), 100);
limited(150).catch(console.log); // Output: "Time Limit Exceeded" at t=100ms