How to receive asynchronous operations using Promise in Vue.js

Preface

When developing with Vue.js, we often need to handle asynchronous operations, such as getting data from the server, sending requests, etc. These operations may take some time to complete, and Vue.js supports using Promise to handle asynchronous operations. Therefore, this article will explore how to use Promise to receive asynchronous operations in Vue.js.

What is Promise?

Promise is an object used to handle asynchronous operations, which allows you to better organize and manage code in asynchronous operations. When you need to perform an asynchronous operation, Promise returns an object. This object has three states: pending, fulfilled, and rejected. A Promise object can only be in one of the states and cannot transition from one state to another.

Promise has two core methods: then() and catch(). The then() method is executed when the Promise object is in the completed state, and the catch() method is executed when the object is in the rejected state.

How to use Promise in Vue.js?

Vue.js components usually need to obtain data from the server or perform other asynchronous operations. When we use Promise, we need to define a function and return a Promise object.

Let us assume that we need to make a request to the server, we can use the axios library. The framework of the function is as follows:

function getData() {
  return new Promise(function(resolve, reject) {
    // 异步操作
    axios.get('/api/data')
      .then(function(response) {
        resolve(response.data);
      })
      .catch(function(error) {
        reject(error);
      });
  });
}

In the above code, we first define a function named getData(). This function returns a Promise object and receives asynchronous operations. Asynchronous operations use the axios.get() function to perform an HTTP GET request.

When the axios.get() function gets a response, it calls the .then() method and passes the response data as a parameter to the resolve() function. This will mark the Promise object status as completed.

When the axios.get() function encounters an error, it calls the .catch() method and passes the error as a parameter to the reject() function. This will mark the Promise object status as rejected.

This is the basic framework of a Promise object. We can use this framework to implement many useful functions.

How do Vue.js components use Promise?

For Vue.js components, we can use Promise to manage and handle asynchronous operations. We can define a lifecycle function called mounted() inside the component and use the Promise function in it. The code example is as follows:

export default {
  name: 'MyComponent',
  data () {
    return {
      data: []
    };
  },
  mounted () {
    const self = this;

    getData().then(function(data) {
      self.data = data;
    }).catch(function(error) {
      console.error(error);
    });
  }
};

In the above code example, we first define a property called data in the component definition. Then, in the mounted() lifecycle function, we call the getData() function and use the .then() and .catch() methods to handle asynchronous operations.

We ensure that the component instance is accessible inside the .then() and .catch() methods by using const self = this. In the .then() method, we assign the data to the component’s data property.

This is the basic framework of Vue.js component code using Promise.

Conclusion

In this article, we discussed how Promise is used in Vue.js. Promise is a very useful tool that allows us to better organize and manage code for asynchronous operations.

If you want to learn more about Promise, you can check out the official documentation of Promise. Hope this article can provide you with some help.

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