What are components in vue? Detailed usage explanation

In the world of front-end development, Vue.js is a very popular framework that allows us to build web applications more efficiently. One of the most interesting aspects of Vue.js is its component system, which can help us organize code and improve maintainability and scalability. In this article, we will explain in detail what Vue.js components are and how to create and use them.

What is a Vue.js component?

Vue.js components are reusable Vue instances that can help us split a complex application into multiple smaller, reusable parts. Each component has its own HTML template, JavaScript code, and CSS styles that can be used repeatedly in different pages.

For example, we can divide a simple login form component into the following three components: a form component to enter username and password, a component to verify credentials through the API, and a component to display the login status. Using Vue.js components can make the code easier to maintain and manage.

Creating a Vue.js component

Creating a Vue.js component is very simple. We just need to define a Vue instance and register it through the Vue.component method. Here is an example:

Vue.component('my-component', {
  template: '<div>{{ message }}</div>',
  data: function () {
    return {
      message: 'Hello, World!'
    }
  }
})

In this example, we define a component named my-component. It has a simple HTML template, where message is a variable, which will be dynamically rendered by Vue.js. This template displays a div element with the message "Hello, World!"

Using Vue.js Components

Once you have registered a component, you can use this component in JavaScript and call it in HTML templates. Here is an example of using components:

<div id="app">
  <my-component></my-component>
</div>

In this example, we use the my-component component we just defined in the HTML template. This will cause Vue.js to automatically render this component when the page loads and insert it into the div with the id "app".

Component data

Different from ordinary instances of Vue.js, component instances are independent of each other and they do not share data. This is why we need to use props attributes and $emit methods to pass information between them.

props attribute: The props attribute can help us pass data from one component to another component. For example, we can define a prop named "my-prop" using the following method:

Vue.component('my-component', {
  props: ['myProp'],
  template: '<div>{{ myProp }}</div>'
})

In this component, we define a prop named "myProp" and use it in the template. We can pass the value of this prop from the parent component to the grandchild component so that we can get the value to use in the grandchild component.

$emit method: If you want to pass data from the component to the parent component, you can use the $emit method. For example, in the child component, we can pass the myValue value to the parent component in the following way:

Vue.component('my-component', {
  template: '<button @click="$emit(\&#39;my-event\&#39;, myValue)">Click me</button>',
  data: function () {
    return {
      myValue: 'Hello, World!'
    }
  }
})

In this component, we have defined a button that when the user clicks on it, it will send Trigger an event named "my-event" and pass the myValue value. In the parent component, we can capture events in the following ways:

<my-component @my-event="handleMyEvent"></my-component>

methods: {
  handleMyEvent: function (value) {
    console.log(value) // 'Hello, World!'
  }
}

In this example, we use the @my-event syntax to listen to the my-event event. When the event is triggered, it calls the handleMyEvent method. In this method, we output the value passed from the child component to the parent component.

Summary

Vue.js component is a very useful tool that can help us better organize and manage code. In this article, we gave a brief introduction to what Vue.js components are and how to create, use and pass data. Hopefully this article has provided you with basic knowledge about Vue.js components and given you a deeper understanding of Vue.js.

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