Скачать или смотреть How to Return an Object from a Function with a Promise in JavaScript

Discover how to effectively return an object from a function containing a Promise in JavaScript and retrieve that object in another function.
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This video is based on the question https://stackoverflow.com/q/67394046/ asked by the user 'doamne fereste' ( https://stackoverflow.com/u/15812177/ ) and on the answer https://stackoverflow.com/a/67394220/ provided by the user 'Muhammad Salif' ( https://stackoverflow.com/u/12978980/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Handling Promises in JavaScript: Returning an Object

In the world of asynchronous programming in JavaScript, working with Promises is essential. One common challenge developers face involves returning an object from a function that contains a Promise and using that object in another function. Let's break down this problem and its solution stepwise.

The Problem

You have the following scenario in your JavaScript code:

You have a function, searchdb, that connects to a MongoDB database, retrieves data, and wants to return an object after resolving the Promise.

However, when you call this function from another function, get, the returned value is not as expected; it's undefined.

Here's a snippet of your code for clarity:

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

The get function calling searchdb:

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

The Solution

To return an object from a function containing a Promise and retrieve that object in another function, you'll need to follow these steps:

Step 1: Modify searchdb to Return a Promise

Instead of returning an object directly from searchdb, you should return the Promise itself. Modify your code like this:

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

Step 2: Resolve the Promise and Create the Object

Within the resolved Promise, you can then create and resolve your object, ensuring that you only return the object after the database query completes.

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

Step 3: Handle the Promise in get Function

In your get function, you can now wait for the Promise to resolve using .then() to get your object.

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

Conclusion

By returning a Promise from the searchdb function and ensuring that the object creation logic is within the Promise's scope, you'll be able to access the resolved object in the get function. Remember, working with asynchronous code can sometimes lead to confusion, but following this structured way can make things clearer and more effective.

Never hesitate to reach for additional resources when delving deeper into JavaScript Promises and asynchronous programming. Happy coding!