Code Logo

Async Sequential with await

Published at25 Jul 2026
Created by
JavaScript Functions Hard 0 views
Like0

Write an async JavaScript function that takes a number, doubles it using a simulated asynchronous delay function, then checks if the result is divisible by 4, all using await instead of .then() chains.

The async/await syntax introduced in ES2017 provides a more readable way to work with Promises. An async function always returns a Promise. The await keyword pauses execution of the async function until the awaited Promise settles, then returns the resolved value. This makes asynchronous code read like synchronous code without blocking the event loop.

Async/await is syntactic sugar over Promises and generators. Under the hood, async functions use generators and the Promise pipeline to pause and resume execution. Error handling uses standard try/catch instead of .catch() chains. This makes complex async flows much easier to read and maintain.

Time complexity is O(1) for the transformations. The async/await overhead is minimal — it adds two microtasks per await but does not block the event loop. The Promise.resolve() call creates an immediately resolved Promise.

Edge cases include zero (0*2=0, 0%4=0 -> true), negative numbers, and ensuring the async function correctly awaits each step before proceeding to the next.

Example Input & Output

Example 1
Input
4
Output
true
Explanation

4*2=8, 8%4=0 -> true

Example 2
Input
5
Output
false
Explanation

5*2=10, 10%4=2 -> false

Example 3
Input
0
Output
true
Explanation

0*2=0, 0%4=0 -> true

Example 4
Input
3
Output
false
Explanation

3*2=6, 6%4=2 -> false

Example 5
Input
8
Output
true
Explanation

8*2=16, 16%4=0 -> true

Algorithm Flow

Recommendation Algorithm Flow for Async Sequential with await
Recommendation Algorithm Flow for Async Sequential with await

Solution Approach

function asyncDouble(x) {
  return Promise.resolve(x * 2);
}

async function solution(n) {
  var doubled = await asyncDouble(n);
  return doubled % 4 === 0;
}

Best Answers

javascript - Approach 1
function asyncDouble(x) {
  return Promise.resolve(x * 2);
}

async function solution(n) {
  var doubled = await asyncDouble(n);
  return doubled % 4 === 0;
}