Understanding Async/Await: How to Fix Instant Execution in JavaScript

Learn how to correctly implement `async/await` in JavaScript to control the execution flow of your code. Understand how promises work and avoid instant execution issues in your async functions.
---

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Despite Await the function is being executed instantly

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Understanding Async/Await: How to Fix Instant Execution in JavaScript

JavaScript is a versatile programming language, and one of its most powerful features is how it handles asynchronous operations. If you're diving into async/await, you might find yourself puzzled when your code behaves differently than expected. This post tackles a common issue faced by newcomers: why does a function execute immediately, even with await?

The Problem: Unexpected Immediate Execution

Consider the following code snippet:

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

This code produces the following output:

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

At first glance, you might expect that the code should wait for the checker() function to finish executing before moving on to log 'the end'. However, that’s not what happens here, and it can be confusing.

What’s Going Wrong?

The primary issue is that the checker function is not asynchronous. Here's a breakdown of what happens:

The function checker() executes immediately when called.

The await keyword only delays the execution of an async function if it is waiting on a promise.

The Solution: Introducing Promises

To correctly use await, you need to make your checker function asynchronous. This can be done using a promise. Here’s how you can modify the code:

Revised Code Structure

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

Breakdown of Changes

Returning a Promise: In the revised checker function, we return a new promise that resolves after a timeout. This means checker() will now correctly indicate when it's done.

Using setTimeout: The setTimeout with a delay of 0 is sufficient to yield the execution flow back to JavaScript’s event loop, allowing other code to run in between.

Await the foo function: Instead of calling foo() directly, we now use await foo() within an immediately invoked async function. This ensures that the program waits for foo() to complete before continuing to the next line.

Expected Output

With these changes, the revised code would produce output similar to:

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

The execution order now aligns with your expectations, where the message the end displays only after the asynchronous function has completed.

Conclusion

Debugging asynchronous code can often be tricky, especially when it comes to understanding how promises and async/await interact. By returning a promise and appropriately awaiting your functions, you can control the flow of your JavaScript code effectively.

Whenever you encounter a situation where await doesn’t seem to function as expected, remember: the function needs to return a promise! This subtlety is key to fully leveraging the capabilities of JavaScript's asynchronous programming model.

By keeping these adjustments in mind, you can enhance your skills in async programming and write more predictable, manageable code!