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Learn how to handle JavaScript promises in a sequential manner. This guide guides you through resolving promises one by one, ensuring you're equipped to avoid common pitfalls like "Too many requests."
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Resolving Promises Sequentially in JavaScript: How to Execute Them One by One

As a developer, you may find yourself working with multiple asynchronous operations in JavaScript, particularly when dealing with Promises. One common challenge is fetching data or executing functions in a specific order. In this guide, we will address the issue of executing promises one by one instead of all at once, ensuring that your application behaves as expected without overwhelming resources.

The Problem: Unable to Execute Promises Sequentially

In a situation where we have an array of promises, you might encounter an error when trying to execute them sequentially. Let's take a look at a sample code that reflects this issue:

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The line that generates an error, promises[i]() is not a function, occurs because promises is an array of Promise objects, not functions. When trying to call each promise like a function, you encounter this error.

The Solution: Execute Promises One by One

To handle real-time updates effectively, it is often useful to resolve promises one by one. Here’s how you can modify your approach to achieve this.

Step 1: Create a Request Function

Instead of mapping your mkt array to an array of promises, you can create a dedicated function that handles fetching and processing each market item.

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Step 2: Loop Through Market Items

Next, you can iterate over the mkt array, invoking the request function for each item and awaiting its resolution. This ensures that each promise is fully resolved before proceeding to the next item.

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Key Takeaways

Error Handling: Always handle errors gracefully using try-catch blocks when dealing with asynchronous functions to avoid unexpected crashes.

Sequential Execution: By awaiting each promise in a loop, you manage the execution order and prevent overwhelming the server with too many requests at once.

Maintain Readability: Structuring your code with standalone functions, such as request, keeps your logic clear and manageable.

Conclusion

By following the steps outlined above, you can effectively manage the resolution of promises in JavaScript, ensuring they execute one by one rather than all at once. This method not only helps in real-time applications but also aids in preventing common issues like too many requests. With this knowledge, you can write more robust and efficient asynchronous code.

Now, go ahead, modify your code, and enjoy the seamless execution of promises in your applications!