Global variable definition function implementation method in Vue documentation

Vue.js is a popular JavaScript framework that provides many powerful features and convenient APIs, allowing developers to easily build interactive web applications. In Vue.js development, global variables are a very useful concept that allow us to share the same data and methods between different components. This article mainly introduces the implementation method of global variable definition function provided in Vue documentation.

1. Vue.mixin()

Vue.mixin() is a global function that accepts a mixin object as a parameter. This mixin object contains some options, such as data, methods, computed, watch and other attributes, which can be mounted to the Vue instance and used synchronously in all components. The following is an example:

// 定义一个全局mixin
var myMixin = {
  data: function () {
    return {
      message: 'Hello World!'
    }
  }
}

// 使用mixin
Vue.mixin(myMixin)

// 创建Vue实例
new Vue({
  el: '#app',
  data: {
    otherMessage: 'Goodbye World!'
  },
  mounted: function () {
    console.log(this.message) // 输出 'Hello World!'
  }
})

In the above example, we define a global mixin object myMixin, which contains a data attribute, which contains a message variable. Then we mount this mixin to the global Vue instance through the Vue.mixin() function. Finally, in the Vue instance, we can access the message variable normally, which proves that the mixin has taken effect.

2. Vue.prototype

Vue.prototype is the prototype object of Vue. By adding methods or properties to it, these methods or properties can be added to the Vue instance so that all components can Can be accessed. Here is an example:

// 定义全局方法
Vue.prototype.$myMethod = function () {
  alert('Hello World!')
}

// 使用全局方法
new Vue ({
  el: '#app',
  mounted: function () {
    this.$myMethod() // 输出 'Hello World!'
  }
})

In the above example, we added a global method $myMethod() to the Vue instance through Vue.prototype. Then in the Vue instance, we can call $myMethod() normally and output 'Hello World!'.

3. Vue.directive()

Vue.directive() can create a global directive and apply it to the elements of all components on the page. It accepts two parameters. The first parameter is the instruction name, and the second parameter is an object containing attributes such as bind, update, componentUpdated, inserted, and unbind. The following is an example:

// 定义全局指令
Vue.directive('my-directive', {
  bind: function (el, binding, vnode) {
    el.style.color = '#' + Math.random().toString(16).slice(2, 8)
  }
})

// 使用全局指令
new Vue ({
  el: '#app'
})

In the above example, we use Vue.directive() to define a global directive 'my-directive', which is used to set a random directive to the element bound to it. color value. In the Vue instance, we only need to add the v-my-directive directive to the element, and this directive will automatically take effect.

Summary

To sum up, Vue provides several ways to define and use global variables. Vue.mixin() can use data, methods, computed, watch and other attributes synchronously in all components. Vue.prototype can add global methods, and Vue.directive() can create global directives that act on the elements of all components on the page. These methods are used in different ways, but they can all effectively implement the definition and use of global variables.

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