Скачать или смотреть How to Properly Resolve a Promise in JavaScript with If Statements

Learn how to effectively manage promises in JavaScript, especially when using if statements within asynchronous functions. This guide provides clear explanations and refactoring techniques to ensure your promises resolve correctly.
---
This video is based on the question https://stackoverflow.com/q/68362785/ asked by the user 'Jennics' ( https://stackoverflow.com/u/13781440/ ) and on the answer https://stackoverflow.com/a/68363299/ provided by the user 'slebetman' ( https://stackoverflow.com/u/167735/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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: can you resolve a promise in an if statement?

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Understanding Promises in JavaScript

JavaScript is a powerful language that allows for asynchronous programming, primarily through the use of promises. A common question that arises, especially for new developers, is: Can you resolve a promise in an if statement?

If you're trying to execute a function that relies on another function's completion using promises, you might run into some issues—like the one faced by an anonymous programmer. They've implemented a function that utilizes a setTimeout command within an if statement, but the promise doesn't seem to resolve correctly. Let's unravel this problem and explore how to correctly handle promises when using conditional statements.

The Problem

In the provided code, the developer is attempting to change a texture on a toaster animation using promises. However, the nested calls to changeTexture create a new promise each time, leading to issues with resolving the original promise intended for the outside function.

Here’s a simplified explanation of what happens with their implementation:

The changeTexture function returns a promise.

A recursive call is made to changeTexture if a condition is met.

Each recursive call creates a new promise that has its own resolve function, disconnected from the first one.

Key Takeaway

The nested structure leads to confusion as the original promise is not effectively linked to the eventual resolve call.

The Solution

To ensure your promise resolves correctly, you need to manage closures and avoid recursive calls that create separate promises. Here are effective strategies to fix the problem:

1. Use an Arrow Function to Maintain Closure

By restructuring the code to avoid recursion, you can simplify the logic. Here’s how you do it:

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

Explanation:

The loop function keeps checking the state and moving towards the resolve condition without creating new promises.

Using an arrow function helps maintain the context of this, ensuring your class properties are accessed as expected.

2. Minimal Code Change Method (Not Recommended)

If you want a quick fix but don’t mind leaving some deprecated code, you can use arguments.callee as follows:

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

Important Note:

While this code may work, the use of arguments.callee has been deprecated in strict mode and is not considered best practice. Always prefer the clearer method of creating dedicated handling functions.

Conclusion

In summary, if you are asking can you resolve a promise in an if statement, the answer is yes, but with proper structure. Keeping your promises manageable and ensuring that you don't create new, unlinked promise scopes is crucial in asynchronous JavaScript.

By refactoring your promise-based code to use stable references and closures, you can avoid common pitfalls and make your code cleaner and more maintainable.

Final Thoughts

As you continue to explore JavaScript and promises, remember these strategies and always strive for clarity and simplicity. Happy coding!