Summary of JavaScript asynchronous programming experience: Tips on using Promise and Async/Await

Summary of JavaScript asynchronous programming experience: Tips for using Promise and Async/Await

Introduction:
With the development of web applications, JavaScript asynchronous programming has become more and more important. In JavaScript, we often need to handle some asynchronous operations, such as initiating HTTP requests, reading files, scheduled tasks, etc. In order to better manage these asynchronous operations, JavaScript provides two mechanisms: Promise and Async/Await. This article will summarize some tips for using Promise and Async/Await to help you better apply them in actual development.

1. Tips for using Promise

1. Use Promise.resolve() and Promise.reject() to quickly create Promise objects
   Promise.resolve() and Promise.reject( ) are two shortcut methods for creating Promise objects. If we need to immediately create a Promise that has been successfully resolved, we can use the Promise.resolve() method; if we need a Promise that has been rejected, we can use the Promise.reject() method.
2. Promise chain calling to avoid callback hell
   Promise supports chain calling. Multiple Promises can be linked through the .then() method to solve the problem of callback hell. Each .then() method returns a new Promise object, which can continue to call the next .then() method. This chain of calls can improve code readability and maintainability.
3. Usage of Promise.all() and Promise.race()
   Promise.all() can wrap multiple Promise objects into a new Promise object. Only when all Promise are resolved, It is finally resolved; and Promise.race() wraps multiple Promise objects into a new Promise object. As long as one Promise is resolved or rejected, it will be finally resolved or rejected.
4. Use the .catch() method to catch exceptions
   In a Promise chain, use the .catch() method to capture exceptions that occur when any Promise in the chain is resolved or rejected. In the .catch() method, you can handle the exception or continue to throw the exception.
5. Promise error handling
   When a Promise object is rejected, the reason for the rejection can be handled by registering the second parameter of the .reject() method. This helps us better track and handle errors.

2. Async/Await usage skills

1. async function and await keyword
   The async function is a syntax sugar introduced by ES7 to simplify Promise usage of. Inside the async function, use the await keyword to pause the execution of the function and wait for a Promise to be resolved before continuing execution. The async function returns a Promise object, and the intermediate result can be obtained through the .then() method.
2. Error handling
   In async functions, you can use try-catch statements to catch exceptions in asynchronous operations. Handle exceptions in a catch block by using the await keyword in the try block to wait for the result of a Promise being resolved or rejected.
3. Concurrent execution of multiple asynchronous tasks
   By using the Promise.all() method combined with the await keyword, multiple asynchronous tasks can be executed concurrently. Wrap multiple Promise objects into an array and use the await keyword to wait for the result of Promise.all(). This allows multiple tasks to be executed in parallel and improves efficiency.
4. Control flow
   In async functions, you can use control flow syntax such as conditional statements and loop statements to implement complex asynchronous operations. This gives us more freedom to organize and control the order of asynchronous operations.

3. Conclusion
Through the introduction of this article, we have learned about the usage skills of Promise and Async/Await in JavaScript asynchronous programming. Promise can better manage asynchronous operations through chain calls, Promise.all(), Promise.race() and other methods. Async/Await provides a more concise and intuitive syntax to handle asynchronous operations. When we encounter asynchronous situations in development, choosing an appropriate way to handle asynchronous operations will improve the readability and maintainability of the code. I hope this article can be helpful to you and help you better apply Promise and Async/Await in actual development.

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