How to Pause Code Execution Until a Function with a Promise Completes in JavaScript

Discover how to properly pause execution in JavaScript code using promises, ensuring cleaner and more efficient programming.
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How to Pause Code Execution Until a Function with a Promise Completes in JavaScript

When writing JavaScript, especially in an asynchronous environment, developers often face challenges related to promise handling. One common issue is wanting to pause code execution until a function using a promise has finished executing. In this guide, we will dive into this issue and explore a solution that upholds clean and reusable coding practices.

The Problem at Hand

You are likely familiar with reusable functions. In this case, you are creating a function named getNumberOfCountriesDownloaded(). This function is designed to calculate how many countries you have downloaded based on their codes stored in local storage. The challenge arises when you find that calling this function does not yield the expected result. Instead, the subsequent lines of code execute immediately, resulting in a variable capturing the output of this function being undefined.

What’s Happening?

When you call getNumberOfCountriesDownloaded(), it initiates a promise.

However, JavaScript does not automatically pause execution until the promise is resolved.

This leads to further code execution without the awaited result of the promise, which can be quite confusing.

The Solution: Making Your Function Return a Promise

To address this issue, the solution lies in ensuring that your getNumberOfCountriesDownloaded() function itself returns a promise. This allows you to leverage the await keyword in other parts of your code, effectively pausing execution until the promise is resolved. Here’s how you can adjust your code:

Updated Function Code

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

Explanation of the Code Adjustments

Return the Promise:

This change signals to JavaScript that further actions depending on this function must await its resolution.

Using async/await:

In your calling function, you can now use await to stop execution until the promise resolves.

Example Implementation

Here’s how you can implement the updated function in your existing code:

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

Benefits of Returning a Promise

Cleaner Code: By returning a promise, your code remains tidy and straightforward. You avoid deep nesting and callback hell.

Better Asynchronous Management: You gain complete control over the asynchronous flow of your application, allowing for guaranteed data handling before proceeding.

Conclusion

In JavaScript, managing asynchronous code can be tricky, especially when dealing with promises. By ensuring that your functions return a promise when needed, you create cleaner code while maintaining the integrity of functionality. The patterns of using async and await promote well-structured and easy-to-read code, ultimately improving your development experience.

Implement these practices in your code today and watch as your programming becomes more efficient!