Скачать или смотреть How to Wait for Promises to Resolve in JavaScript

Discover how to ensure your JavaScript functions wait for asynchronous data, like geocoding coordinates, by mastering Promises and async/await patterns.
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This video is based on the question https://stackoverflow.com/q/64074796/ asked by the user 'mobes' ( https://stackoverflow.com/u/7983153/ ) and on the answer https://stackoverflow.com/a/64074916/ provided by the user 'Dipen Shah' ( https://stackoverflow.com/u/1177814/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Wait for Promises to Resolve in JavaScript: A Guide for Beginners

When dealing with asynchronous operations in JavaScript, especially when working with APIs, developers often encounter a common problem: how to make a function wait for a promise to resolve before continuing execution. This situation frequently arises when fetching data that another operation depends on—like converting an address into geographical coordinates before searching for related events.

If you've found yourself facing such an issue, worry not! In this guide, we'll explore two approaches to effectively handle asynchronous operations in JavaScript using Promises and async/await syntax. Let’s dive in!

The Problem: Asynchronous Behavior in JavaScript

Imagine you have a function that uses a geocoding API to translate user input (like an address or ZIP code) into geographical coordinates. Another function relies on these coordinates to fetch relevant event data. The challenge arises because the geocoding API call is asynchronous. As a result, your event-fetching function may attempt to retrieve the coordinates before the geocoding API has returned a response.

Here is the original code snippet to illustrate the issue:

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The Solution: Handling Promises

To make sure that your function waits for the promise to resolve before proceeding, let's explore two effective approaches: using Promises directly and utilizing the async/await syntax.

Approach 1: Return a Promise

You can modify your toLatLng function to return a promise, which allows you to handle the asynchronous behavior more efficiently.

Updated Code Snippet

Here's how to modify the toLatLng function to return a promise:

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Approach 2: Using Callback Functions

Another method is to use callback functions to manage success and failure scenarios. This can be useful if you prefer to avoid Promises altogether.

Updated Code Snippet

Here’s how you might implement the callback approach:

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Conclusion

In conclusion, whether you choose to work with promises or callback functions, understanding how to manage asynchronous operations is crucial in JavaScript development. Adopting these strategies will help ensure that your application functions as expected, even when dealing with data that takes time to fetch.

Now you can tackle asynchronous behavior with confidence! If you have any further questions or need more examples, feel free to reach out. Happy coding!