1、自定义指令钩子函数
Vue.directive('my-directive', { bind: function () { // 做绑定的准备工作 // 比如添加事件监听器，或是其他只需要执行一次的复杂操作 }, inserted: function (newValue, oldValue) { // 被绑定元素插入父节点时调用 }, update: function (newValue, oldValue) { // 根据获得的新值执行对应的更新 // 对于初始值也会被调用一次 }, unbind: function () { // 做清理工作 // 比如移除在 bind() 中添加的事件监听器 } })指令定义函数提供了几个钩子函数（可选）：
bind: 只调用一次，指令第一次绑定到元素时调用，用这个钩子函数可以定义一个在绑定时执行一次的初始化动作。inserted: 被绑定元素插入父节点时调用（父节点存在即可调用，不必存在于 document 中）。update: 所在组件的 VNode 更新时调用，但是可能发生在其孩子的 VNode 更新之前。指令的值可能发生了改变也可能没有。但是你可以通过比较更新前后的值来忽略不必要的模板更新 (详细的钩子函数参数见下)。componentUpdated: 所在组件的 VNode 及其孩子的 VNode 全部更新时调用。unbind: 只调用一次， 指令与元素解绑时调用。 接下来我们来看一下钩子函数的参数 (包括 el，binding，vnode，oldVnode) 。2、钩子函数参数
钩子函数被赋予了以下参数：
el: 指令所绑定的元素，可以用来直接操作 DOM 。binding: 一个对象，包含以下属性： name: 指令名，不包括 v- 前缀。value: 指令的绑定值， 例如： v-my-directive=”1 + 1”, value 的值是 2。oldValue: 指令绑定的前一个值，仅在 update 和 componentUpdated 钩子中可用。无论值是否改变都可用。expression: 绑定值的字符串形式。 例如 v-my-directive=”1 + 1” ， expression 的值是 “1 + 1”。arg: 传给指令的参数。例如 v-my-directive:foo， arg 的值是 “foo”。 modifiers: 一个包含修饰符的对象。 例如： v-my-directive.foo.bar, 修饰符对象 modifiers 的值是 { foo: true, bar: true }。vnode: Vue 编译生成的虚拟节点oldVnode: 上一个虚拟节点，仅在 update 和 componentUpdated 钩子中可用。3、VNode接口
export default class VNode { tag: string | void; data: VNodeData | void; children: ?Array<VNode>; text: string | void; elm: Node | void; ns: string | void; context: Component | void; // rendered in this component's scope functionalContext: Component | void; // only for functional component root nodes key: string | number | void; componentOptions: VNodeComponentOptions | void; componentInstance: Component | void; // component instance parent: VNode | void; // component placeholder node raw: boolean; // contains raw HTML? (server only) isStatic: boolean; // hoisted static node isRootInsert: boolean; // necessary for enter transition check isComment: boolean; // empty comment placeholder? isCloned: boolean; // is a cloned node? isOnce: boolean; // is a v-once node? asyncFactory: Function | void; // async component factory function asyncMeta: Object | void; isAsyncPlaceholder: boolean; ssrContext: Object | void; constructor ( tag?: string, data?: VNodeData, children?: ?Array<VNode>, text?: string, elm?: Node, context?: Component, componentOptions?: VNodeComponentOptions, asyncFactory?: Function ) { this.tag = tag this.data = data this.children = children this.text = text this.elm = elm this.ns = undefined this.context = context this.functionalContext = undefined this.key = data && data.key this.componentOptions = componentOptions this.componentInstance = undefined this.parent = undefined this.raw = false this.isStatic = false this.isRootInsert = true this.isComment = false this.isCloned = false this.isOnce = false this.asyncFactory = asyncFactory this.asyncMeta = undefined this.isAsyncPlaceholder = false } // DEPRECATED: alias for componentInstance for backwards compat. /* istanbul ignore next */ get child (): Component | void { return this.componentInstance } } export const createEmptyVNode = (text: string = '') => { const node = new VNode() node.text = text node.isComment = true return node } export function createTextVNode (val: string | number) { return new VNode(undefined, undefined, undefined, String(val)) } // optimized shallow clone // used for static nodes and slot nodes because they may be reused across // multiple renders, cloning them avoids errors when DOM manipulations rely // on their elm reference. export function cloneVNode (vnode: VNode, deep?: boolean): VNode { const cloned = new VNode( vnode.tag, vnode.data, vnode.children, vnode.text, vnode.elm, vnode.context, vnode.componentOptions, vnode.asyncFactory ) cloned.ns = vnode.ns cloned.isStatic = vnode.isStatic cloned.key = vnode.key cloned.isComment = vnode.isComment cloned.isCloned = true if (deep && vnode.children) { cloned.children = cloneVNodes(vnode.children) } return cloned } export function cloneVNodes (vnodes: Array<VNode>, deep?: boolean): Array<VNode> { const len = vnodes.length const res = new Array(len) for (let i = 0; i < len; i++) { res[i] = cloneVNode(vnodes[i], deep) } return res }4、VNode
不存在父节点：
存在父节点：
v-IME自定义指令示例：
import { log } from 'SUtil' const install = Vue => { let isBind = true let IMEService = '' let $this = new Vue({ data () { return { outEl: null, outVnode: null } }, watch: { outVnode (value, oldValue) { if (oldValue) { oldValue.componentInstance.isFocus = false } } } }) async function openIme (e, option) { log.d('openIme', isBind, $this.$data.outVnode.componentInstance.percentValue) if ($this.$data.outEl && IMEService && isBind) { log.d('open') $this.$data.outEl.target.focus() let ret = await IMEService.open({ type: IMEService[option.type], track: Number.parseInt(option.track), w: Number.parseInt(option.w), h: Number.parseInt(option.h), x: Number.parseInt(option.x), y: Number.parseInt(option.y) }) if (ret.isSuccess) { console.log('输入法开启成功') } } } async function closeIme (e) { log.d('closeIme', isBind, $this.$data.outVnode.componentInstance.percentValue) if ($this.$data.outEl && IMEService && isBind) { log.d('close') $this.$data.outVnode.componentInstance.isFocus = false let ret = await IMEService.close() if (ret.isSuccess) { console.log('输入法关闭成功') } } } Vue.directive('IME', { bind: function (el, binding, vnode) { $this.$data.outVnode = vnode if (window.taf && window.taf.service.IMEService) { IMEService = window.taf.service.IMEService } else { log.e('IMEService 不存在') $this.$data.outVnode.componentInstance.$emit('error', '输入法故障') log.d('error', $this.$data.outVnode.componentInstance.percentValue) } }, inserted: function (el, binding, vnode) { const inputDom = vnode.componentInstance.$el.querySelector('input') if (inputDom) { inputDom.addEventListener('focus', async focusEvent => { log.d('focus') $this.$data.outEl = focusEvent $this.$data.outVnode = vnode vnode.componentInstance.ctrlBlur = true openIme(focusEvent, binding.value) }) inputDom.addEventListener('click', async focusEvent => { log.d('click') $this.$data.outEl = focusEvent $this.$data.outVnode = vnode vnode.componentInstance.ctrlBlur = true openIme(focusEvent, binding.value) }) inputDom.addEventListener('blur', async focusEvent => { log.d('blur') $this.$data.outEl = focusEvent $this.$data.outVnode = vnode vnode.componentInstance.ctrlBlur = false closeIme(focusEvent) }) } isBind = true }, async unbind (el, binding, vnode) { log.d('unbind') if (window.taf && window.taf.service.IMEService) { IMEService = window.taf.service.IMEService } else { log.e('IMEService 不存在') $this.$data.outVnode.componentInstance.$emit('error', 'IMEService 不存在') log.d('error', $this.$data.outVnode.componentInstance.percentValue) } const inputDom = vnode.componentInstance.$el.querySelector('input') if (inputDom) { inputDom.removeEventListener('click', openIme) isBind = false await IMEService.close() } } }) } export default { install }