# 2637. Promise Time Limit

###### tags: `leetcode 30 days js challenge` `Easy`

[2637. Promise Time Limit](https://leetcode.com/problems/promise-time-limit/)

### 題目描述

Given an asynchronous 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.

### 範例

**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`

### 解答

#### TypeScript

function timeLimit(fn: Fn, t: number): Fn {
  return async function (...args) {
    return new Promise(async (resolve, reject) => {
      const timer = setTimeout(() => {
        reject('Time Limit Exceeded');
      }, t);

      fn(...args)
        .then((res) => {
          clearTimeout(timer);
          resolve(res);
        })
        .catch((err) => {
          clearTimeout(timer);
          reject(err);
        });
    });
  };
}

使用 `Promise.race` 方法

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

    return Promise.race([fn(...args), timer]);
  };
}

> [name=Sheep][time=Tues, May 16, 2023]

### Reference

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