The official order

The primary responsibility of a directive is to apply some behavior to the DOM when the value of its expression changes

v-model

Data binding for forms (input)
V-model implementation: value setting and input event monitoring
Most forms-class components should have a V-Model, such as input fields, checkboxes, checkboxes, and drop-down selectors

V-html: outputs only HTML

Note: If user-generated content is output using V-HTML, it may lead to XSS attacks.
Therefore, to process user-submitted content on the server side, Angle brackets “<>” can be escaped

v-pre

To display the {{}} tag without substitution, use the V-pre to skip compilation of this element and its children

v-bind

Dynamically update attributes on HTML elements; Grammar sugar: 🙂
V-bind binds to class and style

v-on

Bind event listeners; Grammar sugar :(@)

v-cloak

{{message}} will appear on the page when the Vue. Js file is not finished loading. DOM will not be replaced until the Vue instance is created and the template is compiled
In the project, the HTML structure is just an empty div element, and the rest is done by routing to mount different components, so v-cloak is no longer needed

v-once

A defined element or component is rendered only once, including all child nodes of the element or component. The first selection is then, no longer re-rendered as the data changes, treated as static content.
Rarely used unless further performance optimization is required

v-if

Reuse existing elements as much as possible rather than re-render them, which can be avoided by using keys

v-show

Change the element’s CSS property display, which cannot be in<template>Use on labels

Difference between V-if and V-show:

V-if is suitable for scenarios where conditions do not change often, because switching costs are relatively high
V-show is suitable for frequent switching conditions

v-for

Vue maximizes the reuse of DOM elements. Items with the same elements in the replaced array are not rerendered, so you can boldly replace the old array with a new one without worrying about performance.

Problem: Array does not recognize app.books[3]= {… } operation
Fix: use vue. set or this.$set or app.books.splice
Problem: Array does not recognize app.books.length=1 operation
Solution: app. Books. Splice (1)

Custom instruction

website

Global definitions

Vue.directive('focus', {
  // Command options
})
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Local registration

let app = new Vue({
  el: '#app'.directives: {
    focus: {
      // Command options}}})Copy the code

v-focus

<! DOCTYPEhtml>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="Width = device - width, initial - scale = 1.0">
  <title>Vue sample</title>

</head>

<body>
  <div id="app">
    <input type="text" v-focus>
  </div>
  <script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
  <script>
    Vue.directive('focus', {
      inserted: function(el) { el.focus(); }})let app = new Vue({
      el: '#app',})</script>
</body>

</html>
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Use instruction parameters

<! DOCTYPEhtml>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="Width = device - width, initial - scale = 1.0">
  <title>Vue sample</title>

</head>

<body>
  <div id="app">
    <div v-test:msg.a.b="message"></div>
  </div>
  <script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
  <script>
    Vue.directive('test', {
      bind: function(el, binding, vnode){
        let keys = [];
        for(let i in vnode){
          keys.push(i);
        }
        el.innerHTML = 
          'name: ' + binding.name + '<br>' + 
          'value: ' + binding.value + '<br>' + 
          'expression: ' + binding.expression + '<br>' + 
          'argument: ' + binding.arg + '<br>' + 
          'modifiers: ' + JSON.stringify(binding.modifiers) + '<br>' + 
          'vnode keys: ' + keys.join(', ')}})let app = new Vue({
      el: '#app'.data() {
        return {
          message: 'message'}}})</script>
</body>

</html>
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Pull-down menu that can be closed from outside (actual combat)

<! DOCTYPEhtml>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="Width = device - width, initial - scale = 1.0">
  <title>Pull-down menu that can be closed from the outside</title>
  <link rel="stylesheet" type="text/css" href="style.css">

</head>

<body>
  <div id="app" v-cloak>
    <div class="main" v-clickoutside="handleClose">
      <button @click="show = ! show">Click to display the drop-down menu</button>
      <div class="dropdown" v-show="show">
        <p>Drop down the contents of the box and click on the outer area to close it</p>
      </div>
    </div>
  </div>
  <script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
  <script>
    Vue.directive('clickoutside', {
      bind: function (el, binding, vnode) {
        function documentHandler(e) {
          if (el.contains(e.target)) { // The area clicked is inside the element where the instruction is located
            return false
          }
          if (binding.expression) { // Whether there is an expression
            binding.value(e)
          }
        }
        el.__vueClickOutside__ = documentHandler
        document.addEventListener('click', documentHandler)
      },
      unbind: function (el, binding) {
        document.removeEventListener('click', el.__vueClickOutside__)
        delete el.__vueClickOutside__
      }
    })
    // Exercise 1: Support expression updates in update hooks
    // Exercise 2: Extend clickoutside.js to display the dropdown menu by pressing ESC on the keyboard after clicking the button
    // You can also close the drop-down menu
    // Exercise 3: Make exercise 2's ESC button off optional. Prompt, use modifiers such as V-clickoutside. esc
    let app = new Vue({
      el: '#app'.data: {
        show: false
      },
      methods: {
        handleClose() {
          this.show = false}}})</script>
</body>

</html>
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[v-cloak] {
  display: none;
}

.main {
  width: 125px;
}

button {
  display: block;
  width: 100%;
  color: #fff;
  background-color: #39f;
  border: 0;
  padding: 6px;
  text-align: center;
  font-size: 12px;
  border-radius: 4px;
  cursor: pointer;
  outline: none;
  position: relative;
}

button:active {
  top: 1px;
  left: 1px;
}

.dropdown {
  width: 100%;
  height: 150px;
  margin: 5px 0;
  font-size: 12px;
  background-color: #fff;
  border-radius: 4px;
  box-shadow: 0 1px 6px rgba(0.0.0.2);
}

.dropdown p {
  display: inline-block;
  padding: 6px;
}
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Real-time time conversion command (actual combat)

<! DOCTYPEhtml>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="Width = device - width, initial - scale = 1.0">
  <title>Time switch instruction</title>


</head>

<body>
  <div id="app" v-cloak>
    <div v-time="timeNow"></div>
    <div v-time="timeBefore"></div>
  </div>
  <script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
  <script src="time.js"></script>
  <script>
    Exercise 1: Develop a custom directive v-birthday that takes a timestamp of the date of birth and converts it to XXX days old
    // Exercise 2: Extend exercise 1's custom v-birthday instruction to convert XXX days of birth to a specific age, such as 25
    // 8 months and 10 days
    let app = new Vue({
      el: '#app'.data: {
        timeNow: (new Date()).getTime(),
        timeBefore: 1488930695721 / / 2017-03-08
      },
      methods: {
        handleClose() {
          this.show = false}}})</script>
</body>

</html>
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let Time = {
  // Get the current timestamp
  getUnix() {
    let date = new Date(a);return date.getTime();
  },
  // Get the timestamp of today's 0:0:0
  getTodayUnix() {
    let date = new Date()
    date.setHours(0)
    date.setMinutes(0)
    date.setSeconds(0)
    date.setMilliseconds(0)
    return date.getTime();
  },
  // Get the timestamp of 00:00 00:00 on January 1 of this year
  getYearUnix() {
    let date = new Date()
    date.setMonth(0)
    date.setDate(1)
    date.setHours(0)
    date.setMinutes(0)
    date.setSeconds(0)
    date.setMilliseconds(0)
    return date.getTime();
  },
  // Get the standard year month day
  getLastDate(time) {
    let date = new Date(time)
    let month = date.getMonth() + 1 < 10
      ? '0' + (date.getMonth() + 1)
      : date.getMonth() + 1
    let day = date.getDate() < 10
      ? '0' + date.getDate()
      : date.getDate()
    return date.getFullYear() + The '-' + month + "-" + day;
  },
  // Convert the time
  getFormatTime(timestamp) {
    let now = this.getUnix();             // The current timestamp
    let today = this.getTodayUnix();      // Today 0 o 'clock timestamp
    let year = this.getYearUnix();        // This year 0 o 'clock timestamp
    let timer = (now - timestamp) / 1000  // Convert to a second timestamp
    let tip = ' '
    if (timer <= 0) {
      tip = 'just'
    } else if (Math.floor(timer / 60) < =0) {
      tip = 'just'
    } else if (timer < 3600) {
      tip = Math.floor(timer / 60) + 'Minutes ago'
    } else if (timer >= 3600 && (timestamp - today >= 0)) {
      tip = Math.floor(timer / 3600) + 'Hours ago'
    } else if (timer / 86400< =31) {
      tip = Math.ceil(timer / 86400) + 'days ago'
    } else {
      tip = this.getLastDate(timestamp)
    }
    return tip;
  }
}

Vue.directive('time', {
  bind: function (el, binding) {
    el.innerHTML = Time.getFormatTime(binding.value)
    el.__timeout__ = setInterval(() = > {
      el.innerHTML = Time.getFormatTime(binding.value)
    }, 60000);
  },
  unbind: function (el) {
    clearInterval(el.__timeout__)
    delete el.__timeout__
  }
})
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Vue uses three instructions and computed properties

The official order

v-model

V-html: outputs only HTML

v-pre

v-bind

v-on

v-cloak

v-once

v-if

v-show

v-for

Custom instruction

Global definitions

Local registration

v-focus

Use instruction parameters

Pull-down menu that can be closed from outside (actual combat)

Real-time time conversion command (actual combat)

Vue uses three instructions and computed properties

The official order

v-model

V-html: outputs only HTML

v-pre

v-bind

v-on

v-cloak

v-once

v-if

v-show

v-for

Custom instruction

Global definitions

Local registration

v-focus

Use instruction parameters

Pull-down menu that can be closed from outside (actual combat)

Real-time time conversion command (actual combat)

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