Скачать или смотреть Understanding the async and await Method in TypeScript with Angular for Better Async Handling

Learn how to effectively utilize `async` and `await` in TypeScript for Angular applications to manage asynchronous code, especially with geolocation and weather data fetching.
---
This video is based on the question https://stackoverflow.com/q/69094949/ asked by the user 'besim' ( https://stackoverflow.com/u/12391029/ ) and on the answer https://stackoverflow.com/a/69095525/ provided by the user 'Andy' ( https://stackoverflow.com/u/16855899/ ) 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: async and await method in typescript (angular)

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 async and await in TypeScript for Angular

When developing Angular applications, you often encounter scenarios where you need to perform asynchronous operations. One common challenge arises when dealing with functions that fetch data, like obtaining the user's location or retrieving weather data based on those coordinates. If these functions aren't managed correctly, it can lead to confusing behavior where one function executes before another completes. In this guide, we'll explore how to effectively use async and await in TypeScript to manage these asynchronous calls seamlessly.

The Problem

Imagine you have two functions in your Angular component:

getLocation(): This function retrieves the user's current geolocation.

getWeatherByCoordinates(): This function fetches weather data based on the latitude and longitude obtained from the first function.

When called in the ngOnInit() lifecycle method, it may seem like getWeatherByCoordinates() runs before getLocation() has finished executing, leading to empty or undefined data. How can we ensure that getWeatherByCoordinates() only runs after getLocation() has successfully completed its task?

The Solution: Using async and await

To address this problem, we can utilize JavaScript's async and await syntax, which allows us to work with Promises in a cleaner and more readable way. Here's how you can implement it.

Step 1: Modify getLocation() to Return a Promise

First, we need to change getLocation() to return a Promise. This way, we can easily resolve the location data once it becomes available.

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

Step 2: Use async in ngOnInit()

Next, we should make our ngOnInit() method asynchronous and use the await keyword before calling getLocation(). This ensures that Angular waits for the Promise to be resolved before executing the next line.

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

The Complete Example

Putting it all together, your updated Angular component will look like this:

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

Alternative Approach Using Callbacks

If you prefer to use callbacks for controlling the execution order, you can alter your getLocation() function to accept a callback function. However, using async/await is often more straightforward and easier to read in modern JavaScript.

Example of Using Callback

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

Conclusion

In summary, the use of async and await in TypeScript makes handling asynchronous code in Angular applications a lot easier. By restructuring your code to wait for the completion of necessary functions, you can prevent unexpected behavior and ensure your application runs smoothly. Whether you choose to use Promises with async/await or callbacks, it's crucial to manage the flow of asynchronous calls effectively.

By implementing these techniques, you'll be able to enhance the user experience of your Angular applications significantly. Happy coding!