Vue.js Mixins Option Merging


Example

When a mixin and the component itself contain overlapping options, they will be “merged” using appropriate strategies. For example, hook functions with the same name are merged into an array so that all of them will be called. In addition, mixin hooks will be called before the component’s own hooks:

var mixin = {
  created: function () {
    console.log('mixin hook called')
  }
}

new Vue({
  mixins: [mixin],
  created: function () {
    console.log('component hook called')
  }
})

// -> "mixin hook called"
// -> "component hook called"

Options that expect object values, for example methods, components and directives, will be merged into the same object. The component’s options will take priority when there are conflicting keys in these objects:

var mixin = {
  methods: {
    foo: function () {
      console.log('foo')
    },
    conflicting: function () {
      console.log('from mixin')
    }
  }
}

var vm = new Vue({
  mixins: [mixin],
  methods: {
    bar: function () {
      console.log('bar')
    },
    conflicting: function () {
      console.log('from self')
    }
  }
})

vm.foo() // -> "foo"
vm.bar() // -> "bar"
vm.conflicting() // -> "from self"

Note that the same merge strategies are used in Vue.extend().