Understanding the async-await Method Call in Angular and TypeScript

Dive into the functionality of `async-await` in Angular and TypeScript, and learn how to correctly implement it for handling asynchronous programming.
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Understanding the async-await Method Call in Angular and TypeScript

Asynchronous programming, particularly in the context of Angular and TypeScript, can often cause confusion for developers unfamiliar with these concepts. This post will help clarify how the async and await keywords work, addressing common challenges and patterns you’ll encounter when dealing with async operations in your Angular applications.

The Problem: Confusion Around async-await

Recently, a user raised a common question regarding their usage of async-await when evaluating method calls in their Angular service and component classes. They needed clarification on whether they were correctly implementing async and await, especially concerning when the results of an asynchronous operation were accessible.

Their Code Implementation

The user shared the following snippets of their TypeScript code:

Service Method

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

Component Method Call

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

Understanding async-await

What is async-await?

async and await are modern JavaScript syntax utilized in these programming languages to handle asynchronous operations efficiently. Here’s a simple breakdown:

async: When you declare a function as async, it will always return a promise. This makes it clear that the function handles operations that might take time to resolve, such as fetching data from an API.

await: This keyword can only be used inside async functions. It pauses the execution of the async function until the promise is settled. Thus, the code following an await will not run until the awaited promise is resolved.

How Does It Work in Their Example?

With these definitions in mind, let’s clarify how the user’s code works:

In the service method, the await keyword pauses the execution of the function until the call to firestore is complete and settles the promise returned by get().

In the component method, when they use await on the service call, the execution will pause until the aestheticEvaluationExist service method resolves. Hence, by the time control returns to the component, the value of isUpdate will already reflect the result from the service.

Simplifying the Code

While the user’s implementation works, combining await with then() can lead to unnecessary complexity. It’s generally better to stick to either one. Here’s how they could write this more cleanly:

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

This single line effectively captures the intended logic without requiring an additional promise handler, making it clearer and easier to read.

Conclusion

By grasping these concepts, you can confidently manage asynchronous programming within your Angular applications, paving the way for more efficient and maintainable code. Happy coding!