Promise Time Limit 非同步 race 超時

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.

Constraints:

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

解法:

這是在介紹超時Timeout的實作，他會給定一個分同步的function 跟超時異常的秒數

當超過這個時間，就扔出一個"Time Limit Exceeded"的字串錯誤

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

const timeLimit = (fn: Fn, t: number) => {
	return async (...args) => {
        return Promise.race([
            new Promise((resolve, reject)=> setTimeout(()=> reject("Time Limit Exceeded"), t)),
            new Promise((resolve)=> setTimeout(()=> resolve(fn(...args))))
        ])
    }
};