How to perform data responsive updates in Vue

How to perform data responsive updates in Vue?

Vue is a popular JavaScript framework that provides the ability to update data responsively, allowing us to easily update data and automatically update views. This article will introduce how to perform data responsive updates in Vue, including using Vue's responsive system, using computed properties, and using Vue's watchers.

Vue's responsive system

Vue's responsive system is the core mechanism for Vue to implement data responsive updates. It uses the() method to hijack the object's properties, so that when these properties change, the view can be automatically updated. Here is a simple example of Vue:

const vm = new Vue({
  el: '#app',
  data: {
    message: 'Hello, Vue!'
  }
});

In this example, we define a Vue instance and set a namemessageattributes. whenmessageVue will automatically update the view when the property changes.

Here is a one used in a Vue templatemessageExample of properties:

<div >
  {{ message }}
</div>

In this example, we<div>Used in the tag{{ message }}syntax to bindmessageproperty. whenmessageVue will automatically update when the attribute changes<div>Content of the tag.

Calculate properties

In addition to using data attributes directly in templates, Vue also provides a way to calculate attributes to update views. A computed attribute is a special attribute whose value is calculated based on other attributes. Computed attributes can cache the calculation results and will only be recalculated if the attributes it depends on change. Here is an example of computed properties:

const vm = new Vue({
  el: '#app',
  data: {
    firstName: 'John',
    lastName: 'Doe'
  },
  computed: {
    fullName: function() {
      return  + ' ' + ;
    }
  }
});

In this example, we define a computed propertyfullName, its value is based onfirstNameandlastNameThe attributes are calculated. whenfirstNameorlastNameVue will automatically update when the attribute changesfullNameThe value of the attribute.

Here is an example of using computed properties in a Vue template:

<div >
  {{ fullName }}
</div>

In this example, we<div>Used in the tag{{ fullName }}syntax to bindfullNameproperty. whenfirstNameorlastNameVue will automatically update when the attribute changesfullNameThe value of the property and update it<div>Content of the tag.

Watcher

In addition to using computed properties, Vue also provides a Watcher mechanism to update views. Watcher is a listener that listens for changes in an expression and executes a callback function when it changes. Here is an example of a Watcher:

const vm = new Vue({
  el: '#app',
  data: {
    message: 'Hello, Vue!'
  },
  watch: {
    message: function(newValue, oldValue) {
      ('message changed from ' + oldValue + ' to ' + newValue);
    }
  }
});

In this example, we define a Watcher that listensmessageChanges in properties and executes callback functions when they change. whenmessageWhen the properties change, Vue will automatically update the view and execute the callback function.

()and()

Vue does not responsively update the view when we update properties in an object or array. To solve this problem, Vue provides()and()Method to update properties in objects and arrays. Here is a use()and()Example of method:

const vm = new Vue({
  el: '#app',
  data: {
    items: []
  },
  methods: {
    addItem: function() {
      ({ name: 'New Item' });
    },
    removeItem: function(index) {
      (index, 1);
    }
  }
});

In this example, we define an array called items and provide a method called addItem and a method called removeItem. When we call the addItem method, it adds a new item named New Item to the items array. When we call the removeItem method, it deletes the item of the specified index from the items array. However, these operations do not responsively update the view.

To solve this problem, we can use()Method to add new items to the array as follows:

addItem: function() {
  (, , { name: 'New Item' });
},

In this example, we use()Method to add new items toitemsin the array.()The method accepts three parameters: the array to add, the index to add, and the item to add.

Similarly, we can use()Method to delete items from the array as follows:

removeItem: function(index) {
  (, index);
}

In this example, we use()Method fromitemsDeletes the item in the array with the specified index.

Summarize

Vue provides a powerful data responsive update mechanism, allowing us to easily update data and automatically update views. This article introduces Vue's responsive system, computed properties, Watcher, and using the () and () methods to update properties in objects and arrays. By learning these, you can better understand Vue's data responsive update mechanism and use it better in actual development.

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