Vue自定义指令及指令定义函数的具体分析（代码）

<p id="app" v-demo:foo.a.b="message"></p>

Vue.directive('demo', {
  bind: function (el, binding, vnode) {
      console.log('bind');
    var s = JSON.stringify
    el.innerHTML =
      'name: '       + s(binding.name) + '<br>' +
      'value: '      + s(binding.value) + '<br>' +
      'expression: ' + s(binding.expression) + '<br>' +
      'argument: '   + s(binding.arg) + '<br>' +
      'modifiers: '  + s(binding.modifiers) + '<br>' +
      'vnode keys: ' + Object.keys(vnode).join(', ')
  }
});
new Vue({
  el: '#app',
  data: {
    message: 'hello!'
  }
});

Vue.directive('color-swatch', function (el, binding) {
  el.style.backgroundColor = binding.value
})

<p v-demo="{ color: 'white', text: 'hello!' }"></p>

Vue.directive('demo', function (el, binding) {
  console.log(binding.value.color) // => "white"
  console.log(binding.value.text)  // => "hello!"
})

<p id="app">
    <my-comp v-if="msg" :msg="msg"></my-comp>
    <button @click="update">更新</button>
    <button @click="uninstall">卸载</button>
    <button @click="install">安装</button>
</p>
<script type="text/javascript">
    Vue.directive('hello', {
        bind: function (el){
            console.log('bind');
        },
        inserted: function (el){
            console.log('inserted');
        },
        update: function (el){
            console.log('update');
        },
        componentUpdated: function (el){
            console.log('componentUpdated');
        },
        unbind: function (el){
            console.log('unbind');
        }
    });

    var myComp = {
        template: '<h1 v-hello>{{msg}}</h1>',
        props: {
            msg: String
        }
    }

    new Vue({
        el: '#app',
        data: {
            msg: 'Hello'
        },
        components: {
            myComp: myComp
        },
        methods: {
            update: function (){
                this.msg = 'Hi';
            },
            uninstall: function (){
                this.msg = '';
            },
            install: function (){
                this.msg = 'Hello';
            }
        }
    })
</script>

import store from '@/store'

export default {
  inserted(el, binding, vnode) {
    const { value } = binding
    const roles = store.state.permission.pagePermission
    if (value && typeof value === 'string' && value.length > 0) {
      const hasPermission = roles.some(role => {
        return role.permission == value
      })
      if (!hasPermission) {
        el.parentNode && el.parentNode.removeChild(el)
      }
    } else {
      throw new Error(`need roles! Like v-permission="'button'"`)
    }
  }
}

import permission from './permission'

const install = function(Vue) {
  Vue.directive('permission', permission)
}

if (window.Vue) {
  window['permission'] = permission
  Vue.use(install) // eslint-disable-line
}

permission.install = install
export default permission