Скачать или смотреть How to Check for Null Values Before Using Promise.all in JavaScript

Discover a simple method to handle null values in your GET requests using `Promise.all` in JavaScript, ensuring efficient and error-free code execution.
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This video is based on the question https://stackoverflow.com/q/77710266/ asked by the user 'engForLife' ( https://stackoverflow.com/u/3927069/ ) and on the answer https://stackoverflow.com/a/77710349/ provided by the user 'Asad Gulzar' ( https://stackoverflow.com/u/12291046/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Handling Null Values in Promise.all in JavaScript

When working with asynchronous operations in JavaScript, Promise.all is a powerful method for executing multiple promises concurrently. However, it can become challenging wanneer certain inputs are null. In this guide, we’ll explore how to effectively handle these null values when you want to prevent unnecessary API calls, ensuring your code remains clean and efficient.

Understanding the Problem

In certain situations, you may want to execute GET requests that depend on variables, such as IDs. However, if any of these variables are null, executing those requests could result in unnecessary computations or errors. For example, consider the following code snippet:

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

Here, if variable1, variable2, or variable3 are null, you will end up making requests that are not only futile but may also complicate error handling in your application.

Solution Overview

To address this issue, we can introduce a conditional check before we initiate our API requests. Instead of calling client.getL, client.getF, or client.getT directly, we will create an array of promises where each promise is based on the corresponding variable. This ensures that if a variable is null, its promise will be null, thereby not attempting to execute the API call.

Implementing the Solution

Here's how you can implement this:

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

Breakdown of the Code

Creating Promises Array:

We create an array promises where each element is determined by a conditional statement.

The syntax variable1 !== null ? client.getL(variable1) : null checks if variable1 is not null.

If it is not null, it calls client.getL(variable1), otherwise, it sets the value to null.

Awaiting the Results:

Next, we pass the promises array to Promise.all.

This function resolves the promises concurrently. If a promise is null (as in the case where the variable was null), it will simply skip that promise.

Result Assignment:

Finally, we use destructuring to assign the results to L, P, and T. If any of the API calls were not executed because the corresponding variable was null, the corresponding results will also be null.

Conclusion

This simple yet effective technique allows JavaScript developers to gracefully handle null values in their asynchronous code. By leveraging conditional statements to build the promises array, you can avoid unnecessary API calls and ensure your application runs smoothly.

Such practices not only optimize the performance of your code but also enhance readability, making it easier to maintain in the long run. So the next time you're dealing with multiple asynchronous requests, remember to check for null values first!