Mastering Promise Results with for Loops in ExpressJS and TypeScript скачать в хорошем качестве

Mastering Promise Results with for Loops in ExpressJS and TypeScript

Learn how to effectively manage asynchronous operations in ExpressJS using TypeScript by assigning `for` loop promise results to an external variable. --- This video is based on the question https://stackoverflow.com/q/73805312/ asked by the user 'xTchan' ( https://stackoverflow.com/u/16697983/ ) and on the answer https://stackoverflow.com/a/73805375/ provided by the user 'Mina' ( https://stackoverflow.com/u/11887902/ ) 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: How to assign for loop promise result to the outside variable in Expressjs, Typescript? 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. --- Mastering Promise Results in ExpressJS and TypeScript When working with asynchronous operations in JavaScript, handling promises can become tricky, especially within for loops. This guide tackles a common problem: How to assign the results of a loop that handles promises to an external variable in an ExpressJS application using TypeScript. The Problem Imagine you have a function that queries an API for details about selected Salesforce objects. You want to loop through these objects, gather their details, and return them to the client. However, using a regular forEach loop with promises leads to unexpected results because the loop completes before the promises are resolved. This leads to returning an empty array or incorrect data. The Original Code Here's a snippet of what the initial implementation might look like: [[See Video to Reveal this Text or Code Snippet]] As you can see, while the plan is to collect results in sObjectsDetails, the loop will finish execution before any of the promises resolve. Consequently, we'd end up returning sObjectsDetails while it's still empty. The Solution To tackle this issue effectively, we can leverage async/await along with Promise.all. This allows us to wait for all promises to resolve before moving on. Here’s how we can restructure the function: Step-by-Step Breakdown Change the Loop to map: Instead of using forEach, we can use the map method. This creates an array of promises from our asynchronous calls. Use Promise.all: Promise.all takes an array of promises and resolves them all in parallel. We’ll be able to wait until all promises are finished before we proceed. Await the Results: By using await, we ensure that the results are fully available when we assign them to our external variable. Here’s the revised code: [[See Video to Reveal this Text or Code Snippet]] Key Benefits of the Revised Code Cleaner Code: By using async/await, the flow of the function reads more like synchronous code, making it easier to understand. Efficient Promise Handling: Promise.all resolves all API requests simultaneously, which can greatly improve performance when dealing with multiple objects. Error Management: Using async/await with try/catch (if implemented) provides better error handling and debugging capabilities. Conclusion Handling asynchronous operations properly can be challenging, but using async/await in combination with Promise.all is a powerful way to manage multiple promises effectively. This not only simplifies your code but also enhances performance by allowing for concurrent execution of asynchronous tasks. If you're working with ExpressJS and TypeScript, implementing these patterns will significantly improve your API interactions! Happy coding!