Understanding Async/Await in Node.js: Ensuring Function Execution Order

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When developing applications that rely on asynchronous operations, such as databases or external APIs, the async/await syntax in JavaScript can make your code cleaner and more straightforward. However, many newcomers often run into issues with function execution order, causing confusion when things don’t work as expected. If you're facing this challenge, you’re not alone. Let's explore a recent case where an async function didn't execute in the anticipated order due to a common mistake.

The Problem

[[See Video to Reveal this Text or Code Snippet]]

In this scenario, the output indicates that the showResults function is being called before the loadDashboardFromId function has finished executing and returning a value. Consequently, your results are undefined, leading to frustrating debugging sessions.

Understanding async/await

What is async/await?

async/await is a modern feature of JavaScript that allows you to write asynchronous code in a more synchronous manner. Here's a quick overview of how it works:

async functions always return a promise.

await pauses the execution of the async function until the promise is resolved.

The Issue with Mixing

The problem arises when you mix promise-handling styles, especially using then/catch with await. This can inadvertently create situations where your code execution order is disrupted. In the code example provided, the loadDashboardFromId function uses then to handle the promise from findOne, which creates a separate execution context and does not return the expected result to the calling function.

The Solution

To ensure your async functions execute in the proper order, follow these guidelines:

1. Use await Consistently

Replace any usage of then/catch with await so that your function wait for the promise to resolve before continuing execution. Here's the corrected version of the loadDashboardFromId function:

[[See Video to Reveal this Text or Code Snippet]]

2. Refactor Calling Functions

Make sure that functions that call loadDashboardFromId also use await. Your getDashboardData function remains as is, as it correctly awaits the result from loadDashboard:

[[See Video to Reveal this Text or Code Snippet]]

3. Handle Errors Gracefully

Consider using try/catch around your await calls to manage errors appropriately. This makes your code more robust:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

If you're still encountering issues with your asynchronous code, revisit the way you're structuring your async functions and consider adopting the practices outlined above. Happy coding!