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In Vue projects, we often need to obtain data and process it through asynchronous requests. However, in some cases, we need to wait until all requests are completed before executing the next method, such as rendering a page after data obtained by multiple requests arrives. So in Vue, how do we implement the next method after all requests are completed? This article will introduce how to implement this function in detail.

1. Promise.all()

Promise.all()It is a method in ES6 that can wrap multiple Promise instances into a new Promise instance. When all Promise instances succeed, the new Promise instance will succeed; as long as one fails, the new Promise instance will fail. Therefore, we can use the Promise.all() method to execute the next method after all requests are completed.

Code example:

const promises = [axios.get(url1), axios.get(url2), axios.get(url3)];
Promise.all(promises).then((results) => {
  // After all requests are completed, execute the next method
  nextMethod();
}).catch((error) => {
  console.log(error);
});

In the above code, we use the axios library to send three asynchronous requests, store the Promise instances of these three requests in an array, and use this array as Promise.all()the parameter of . When all requests are completed, Promise.all()a new Promise instance will be returned, and then()the method will be called to execute the next method. If one request fails, the method Promise.all()will be called directly catch().

2. async/await

In addition to using Promise.all()the method, we can also use async/awaitthe syntax to execute the next method after all requests are completed. async/awaitIt is a syntactic sugar in ES7 that can make asynchronous code look like synchronous code, making the code clearer and easier to understand.

Code example:

async function fetchData() {
  const result1 = await axios.get(url1);
  const result2 = await axios.get(url2);
  const result3 = await axios.get(url3);
  // After all requests are completed, execute the next method
  nextMethod();
}

fetchData().catch((error) => {
  console.log(error);
});

In the above code, we use asyncthe function to define a fetchData()function, in which the keyword is used awaitto wait for each asynchronous request to complete. When all requests are completed, fetchData()the function will directly execute the next method. If a request fails, fetchData()the function will throw an exception, and we can use catch()the method to catch the exception.

Note:

1. When using Promise.all()methods or async/awaitsyntax, you must ensure that all asynchronous requests have been sent, otherwise the next method may be executed before the request is completed.
2. If you need to execute the next method after the request is completed, and this method is also asynchronous, we need to use Promise.all()methods or async/awaitsyntax in this method to wait for all asynchronous operations to complete.
3. When using Promise.all()methods, if a request fails, the method Promise.all()will be called directly catch(), and we need to catch()handle the exception in the method; when using async/awaitsyntax, if a request fails, fetchData()the function will throw an exception, and we need to use catch()a method to catch the exception.

Summarize:

In Vue projects, we often need to wait for all asynchronous requests to complete before executing the next method. This article introduces Promise.all()the methods and async/awaitsyntax to achieve this function, and provides code examples and precautions. I hope this article can help you better handle asynchronous requests.