How to use VUe double bracket attributes-Front-end Q&A-php.cn

How to use VUe double bracket attributes

王林

Release： 2023-05-25 11:44:37

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Vue is a popular JavaScript framework that uses double curly braces ("{{" and "}}") syntax to implement data binding between properties and views. Templates in the VUe framework display specific properties of variables monitored by the framework. When the values of these variables change, these properties also change, thereby automatically updating the corresponding values in the view. Double curly bracket attributes are widely used in Vue, so how should we use double square bracket attributes? The following article will briefly introduce it.

Basics of Vue

Before learning the properties of double brackets, we need to understand some basic knowledge of Vue. First of all, the Vue instance is the root instance of the Vue application and it is the entry point of the Vue application. A Vue instance is created by passing an options object to it. This options object contains the Vue instance's data, templates, and methods. The data of a Vue instance can be represented using JavaScript objects. Vue provides a simple template syntax to bind this data to HTML views.

In Vue, we can use double bracket attributes for data binding. The double bracket attribute is a special attribute of Vue. Double curly brackets "{{" and "}}" are used to surround an expression, where the expression can be a JavaScript expression or a Vue expression. When Vue detects a change in the data, it automatically updates the value bound to the double bracket property. Below, we discuss in detail how to use double bracket attributes.

Use of double square bracket attributes

Using double square bracket attributes is very simple. You only need to add double square bracket syntax to the HTML element that needs to bind data, and write the bound attributes in double brackets. For example, we can add double bracket attributes in a tag to bind data in Vue, as shown below:

<div id="app">
  <p>Message: {{ message }}</p>
</div>

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In Vue, we need to use a Vue instance to complete this binding . Here is an example of a Vue instance:

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

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In this example, we use a Vue instance app and bind it to the ID app on DOM elements. We also define the data object of the Vue instance, which includes a string variable named message. This message variable will be used for our double bracket attribute binding in HTML.

In the above example, we can see that we use the "{{ message }}" syntax to bind the message variable. When the data of the Vue instance changes, Vue will automatically re-render the HTML and update the value of this message variable. This is the basis for using double bracket attributes in Vue.

In addition to binding simple text, we can also use the double bracket attribute to bind other types of data. For example, we can bind data types such as arrays, objects, and functions in the Vue instance to double bracket attributes in HTML.

Expressions of double bracket attributes

In Vue, double bracket attributes can contain any JavaScript expression, including arithmetic expressions, conditional statements, function calls, etc. When the variable in the expression changes, the value in the attribute is updated accordingly.

The following is a simple example:

<div id="app">
  <p>Message: {{ message + ' ' + name }}</p>
</div>

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In this example, we splice the message variable and the name variable through expressions, And bind them into a  tag. When the data of the Vue instance changes, the values in the properties are automatically updated.

Limitations of double bracket properties

Although the double bracket property provides a very convenient way to implement data binding, it also has some limitations. First of all, double bracket attributes can only be used within the text content of HTML element nodes. If we need to use data binding in other attributes of element nodes, we need to use other methods provided by Vue, such as the v-bind directive.

In addition, if our web pages require a large number of double bracket attributes, we need to pay attention to performance issues. Because every time the data changes, Vue needs to re-render the entire HTML page to update the changes, which may cause a certain burden on the performance of the page. Therefore, we should reduce the use of double bracket attributes as much as possible to avoid over-rendering the page.

Conclusion

In Vue, double bracket properties provide a convenient way to implement data binding. We can use the double bracket attribute to bind the data in the Vue instance to the element node in the HTML view to achieve automatic page updating. Double bracket attributes can contain any JavaScript expression, providing great flexibility. But we also need to pay attention to the limitations and performance issues of double bracket attributes. By using the double bracket attribute correctly, we can make the page more concise, flexible and efficient.

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