Understanding the async keyword in JavaScript and how it returns a promise

If you’ve ever wrestled with callbacks and messy async flows, the async keyword in JavaScript feels like a little superpower. It streamlines how we write code that waits for other work to finish—without turning our code into a tangled web of nested callbacks. Let’s walk through a small, concrete example and then connect it to bigger ideas you’ll see in modern web development.

A quick quiz to anchor the idea

Question: What is the purpose of the async keyword in JavaScript?

• Choice A: It allows a function to return a promise

• Choice B: It creates a new synchronous function

• Choice C: It declares a variable

• Choice D: It initializes a JavaScript object

Correct answer: Choice A.

Here’s the thing: when you declare a function with async, the function automatically wraps whatever you return in a Promise. That means even if you return a plain value, the runtime converts it into a Promise that resolves to that value. If you return a promise explicitly, that same promise is just handed along.

A simple illustration

Imagine a function that fetches a user profile, but you want to keep the flow clean and readable:

async function getUserProfile(userId) {

const response = await fetch(https://api.example.com/users/${userId});

const profile = await response.json();

return profile;

}

What happens here?

• The function is marked async, so it returns a Promise.

• Inside, await pauses execution until fetch resolves, then until response.json() resolves.

• The final return value (the profile) becomes the resolution value of the Promise.

If you call getUserProfile(123), you don’t get a profile right away. You get a Promise. You can then attach .then(...) handlers or, more often these days, use await again in a higher-level async function:

async function showProfile(userId) {

const profile = await getUserProfile(userId);

console.log(profile.name);

}

Why this is a big deal

• Readability: async/await makes asynchronous code look closer to synchronous code. That means fewer mental gymnastics when you’re reading a function that fetches data, parses it, and uses it to render something on the page.

• Flow control: You can write sequences of asynchronous steps that read like a checklist—fetch, parse, display—without nesting callbacks or chaining a dozen .then calls.

• Error handling: Try/catch works naturally with async/await, just like with synchronous code. If something goes wrong, you can catch it in a familiar way and handle it gracefully.

Error handling, the clean way

Errors tend to sneak in during network requests or data parsing. Here’s how you can handle them with async/await:

async function loadData() {

try {

const resp = await fetch('https://api.example.com/data');

if (!resp.ok) throw new Error('Network response was not ok');

const data = await resp.json();

return data;

} catch (err) {

console.error('Failed to load data:', err);

// You might show a user-friendly message or retry

throw err; // or return a fallback value

}

}

The try/catch pattern keeps things predictable. It’s the same idea you’d use in many programming contexts, which is part of why this approach feels so natural to developers across backgrounds.

Where does async actually matter in real apps?

• API calls: When you fetch data for dashboards, profiles, or search results, async/await helps keep the request logic tidy.

• Sequencing tasks: Sometimes you need a series of steps in order, where each step depends on the result of the previous one. Async/await makes that sequence readable.

• Error resilience: In production apps, you want predictable error behavior. Async/await, paired with try/catch, gives you a familiar rhythm for handling failures.

A peek under the hood

• Async functions always return a Promise. If you don’t return anything, the Promise resolves to undefined. If you return a value, the Promise resolves to that value. If you return a Promise, the async function adopts that Promise’s state (it waits for it to settle).

• Await pauses only the async function, not the entire thread. Other code can run while you’re waiting, which keeps apps responsive.

• You can mix awaiting simple values and awaited promises, but the power really shows when you’re coordinating multiple asynchronous operations.

A few practical patterns to keep in mind

1. Keep async functions focused

Short, purposeful async functions are easier to read and test. If a function starts dragging in several unrelated tasks, consider splitting it into smaller async helpers.

2. Use await for clarity, not just because you can

If two operations don’t depend on each other, you can run them in parallel with Promise.all. It can speed things up and keep code clean.

Example:

async function loadDashboard() {

const [user, settings] = await Promise.all([getUser(), getSettings()]);

// use user and settings together

}

3. Don’t forget error boundaries

If you’re building a UI, think about what happens when a fetch fails. Show a friendly message or a retry option instead of a broken screen.

4. Testable by design

Async/await makes it easier to test asynchronous logic, because you can write tests that await the outcome and assert on the final state or data.

5. Be mindful of environment quirks

Different JavaScript environments handle fetch and Promises in slightly different ways. When you’re building for browsers, you’ll rely on native Promises and the fetch API. In Node.js, you’ll still have Promises, and you might use libraries like axios or node-fetch for similar results. The key idea is the same: you’re asking the runtime to hold for a moment while something else finishes.

A tangential note you might enjoy

If you’re digging into Revature’s curriculum, you’ll notice async/await surfaces a lot because modern apps talk to servers, microservices, or other data sources. Understanding how to coordinate asynchronous work is a foundational skill, much like learning the ropes of a relational database or a frontend framework. It’s less about memorizing a single trick and more about building a mental model: promises represent future results, and async helps you write the code that gets those results without turning your code into a maze.

A tiny mental model you can carry

Think of async as the “pause button” for a single function, not the entire program. Await is the moment you press play again, letting the function resume once the awaited work finishes. If you’ve ever waited in line for coffee and checked your messages in between sips, you’ve already tasted the rhythm of async in action.

Putting it all together

• The purpose of async is simple: it makes a function return a Promise, enabling a cleaner, more readable way to handle asynchronous work.

• Await unlocks a natural flow inside async functions, letting you write code that looks sequential even when it’s not.

• Error handling becomes more straightforward with try/catch, blending familiar programming patterns with modern JavaScript features.

A final nudge

If you’re exploring JavaScript in a learning track or bootcamp, you’ll likely encounter a lot of real-world scenarios where data needs to arrive before a view renders, or where multiple requests run in parallel to speed things up. Mastering async/await gives you a solid toolkit for those moments. It’s one of those topics that starts simple but pays dividends as you build more ambitious apps.

To wrap up, here’s a quick recap you can keep handy:

• async marks a function to return a Promise.

• await pauses that function until the awaited operation settles.

• Try/catch provides a clean way to manage errors.

• Use Promise.all to run independent tasks in parallel when speed matters.

• Keep functions focused and testable, and you’ll find asynchronous code becomes a lot less intimidating.

If you’re curious, you can experiment with a tiny project that fetches data from a public API, processes it, and renders a simple result in the console. You’ll feel the flow shift from callback-heavy code to something more readable and maintainable in no time. And when you see the pattern evolve across different parts of the Revature curriculum, you’ll recognize the same core idea showing up in various guises—promises, awaits, and resilient error handling, all working together to keep apps smooth and responsive.