What are the internal settings of vue

Vue.js is a progressive JavaScript framework that can be used to build interactive web interfaces. With features such as data binding and composability, Vue.js has become one of developers' favorite frameworks. In addition, Vue.js also has rich internal settings, which this article will introduce one by one.

Responsive system

Vue.js’ core reactive system is one of its most powerful features. In Vue.js, when working with data objects, the view re-renders whenever the data changes without the need to manually update it. This is because Vue.js uses a reactive system, which automatically updates views.

The core of the responsive system implemented by Vue.js is the Object.defineProperty() method. It can be used to convert individual properties into getters and setters, thereby automatically updating their associated views when the property value changes.

Here is a basic Vue.js example:

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

In this example, we use the data attribute to create a message named message Attributes. Now, if you change message, Vue.js will automatically update the property value and the view will be automatically updated.

Life cycle hook function

Vue.js has a strict life cycle process, in which each event has a hook function, so that custom behavior can be injected into user-defined code. The main purpose of these life cycles is to execute code at specific stages, for example, during instantiation, during data changes, during destruction, etc.

Life cycle hook functions are divided into two categories: pre-hook and post-hook. During the life cycle of the instance, Vue.js will first call the pre-hook function, and then call the post-hook function when the life cycle of the instance ends.

The following is the life cycle hook function of the Vue.js component:

beforeCreate
created
beforeMount
mounted
beforeUpdate
updated
beforeDestroy
destroyed

Custom events

In Vue.js, you can use custom events to implement component communication . Custom events allow communication between ancestor components and subordinate components. Parent components can trigger custom events through the $emit method, and child components can use the $on method to listen to these events.

The following is an example of using custom events:

// 父组件
Vue.component('button-counter', {
  template: '<button v-on:click="incrementCounter">{{ counter }}</button>',
  data: function () {
    return {
      counter: 0
    }
  },
  methods: {
    incrementCounter: function () {
      this.counter += 1
      this.$emit('increment')
    }
  }
})

// 祖先组件
var app = new Vue({
  el: '#app',
  data: {
    total: 0
  },
  methods: {
    incrementTotal: function () {
      this.total += 1
    }
  }
})

In this example, we define a component named button-counter. This component has an onClick event, and each click will increase the counter by 1. Additionally, it will trigger a custom event named increment on every click and pass it to its ancestor component. This ancestor component can listen to the event using the $on method and increment the total count when the event is received.

Slots

Vue.js allows users to create components more easily by using slots. It allows users to define reusable templates that can be selectively replaced or extended by parent components or ancestor components.

The following is an example of a Vue.js component using slots:

Vue.component('my-component', {
  template: `
<div>
  <h2>This is my component</h2>
  <slot></slot>
</div>
`
})

// 祖先组件
var app = new Vue({
  el: '#app',
  data: {
    message: 'Hello Vue!'
  },
  template: `
<my-component>
  <p>{{ message }}</p>
</my-component>
`
})

In this example, we define a component my-component. A slot <slot></slot> is defined in the component's template. When my-component is used in the ancestor component, the content inside the slot&lt ;p>{{message}}</p> will be inserted into the slot position of the component template.

Filter

In Vue.js, filters are functions that can be used to format output. Filters can be used in double curly brace interpolation and v-bind expressions for formatting text. Vue.js provides some built-in filters, such as: currency, capitalize, uppercase, etc.

The following is an example of a custom filter:

Vue.filter('reverse', function (value) {
  if (!value) return ''
  value = value.toString()
  return value.split('').reverse().join('')
})

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

In this example, we define a custom filter named reverse. When this filter is used to modify a message value, it inverts the value and returns a new result.

Summary

Vue.js is a powerful framework that contains many internal settings. This article introduces Vue.js's responsive system, life cycle hook functions, custom events, slots, filters and other important settings. Learning these settings is very important for Vue.js developers, because mastering these skills will better build high-quality interactive web applications.

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