Why can't Vue respond to array changes?

Vue.js is a very popular front-end framework today. It uses two-way data binding to render and update data. In Vue.js, we can automatically update the view through changes in data, which is also an important feature of Vue.js. However, in Vue.js, sometimes we may encounter a strange problem, that is why Vue.js cannot respond to changes in the array. Next, we will explore the causes of this problem and how to solve it.

Why Vue cannot respond to array changes

In Vue.js, when we change the elements of an array, Vue.js can detect the change. However, when we use an array method to change the array, such as push(), pop(), shift(), unshift(), splice(), etc., Vue.js cannot detect the changes in the array. This problem The reason is due to JavaScript limitations.

In Javascript, all array operations are based on the methods of a primitive Array.prototype object. These methods include push(), pop(), shift(), unshift(), splice(), etc. These methods are all primitive array methods. They can change the contents of the array, but they cannot change the reference of the array. This means that when we use these methods to mutate the array, the reference to the array does not change. Vue.js relies on the observer mode to implement data responsiveness. When the reference of the array does not change, Vue.js cannot detect changes in the array.

For example, we define an array:

data() {
  return {
    list: [1, 2, 3]
  }
}

When we add an element to the array through the following code:

this.list.push(4)

Vue.js cannot detect the array changing. This is why Vue.js cannot respond to array changes. But don't worry, Vue.js provides us with some ways to solve this problem.

How to solve the problem that Vue cannot respond to array changes

Vue.js provides some methods to solve the problem of array changes. These methods include:

1. Use Vue .set() method

Vue.js provides a Vue.set() method, which can be used to add a new property to the responsive object and allow Vue.js to detect it changes in this property. We can use the Vue.set() method to solve the problem of array changes, for example:

Vue.set(this.list, 3, 4)

This method will add a new element to the array list, and Vue.js can detect changes in the array.

2. Use splice() method

We can use the splice() method of the array to change the array. In this way Vue.js can detect changes in the array. . For example:

this.list.splice(3, 0, 4)

This method will insert element 4 into the fourth position of the array list, and Vue.js can detect changes in the array.

3. Add a new array to the array

We can add a new array to the array. This method can also solve the problem of array changes, for example:

this.list = this.list.concat([4])

The result of this is to create a new array and then add the array to the original array. Vue.js can detect changes in arrays.

It should be noted that Vue.js can detect changes to the elements in the array, but Vue.js cannot detect the overall assignment of the array. Therefore, you should try to use the splice() or Vue.set() method when modifying array elements.

Conclusion

In Vue.js, the problem of being unable to respond to array changes is caused by JavaScript limitations. Vue.js provides some methods to solve the problem of array changes, including using the Vue.set() method, splice() method, and adding a new array to the array. Through these methods, we can easily solve the problem of array changes not being able to respond.

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