一、自定义指令

<!DOCTYPE html>
<html>
    <head>
        <meta charset="UTF-8" />
        <title>自定义指令</title>
        <script type="text/javascript" src="../js/vue.js"></script>
    </head>
    <body>
        <!-- 
                需求1:定义一个v-big指令,和v-text功能类似,但会把绑定的数值放大10倍。
                需求2:定义一个v-fbind指令,和v-bind功能类似,但可以让其所绑定的input元素默认获取焦点。
                自定义指令总结:
                        一、定义语法:
                                    (1).局部指令:
                                                new Vue({                                                           new Vue({
                                                    directives:{指令名:配置对象}   或           directives{指令名:回调函数}
                                                })                                                                      })
                                    (2).全局指令:
                                                    Vue.directive(指令名,配置对象) 或   Vue.directive(指令名,回调函数)

                        二、配置对象中常用的3个回调:
                                    (1).bind:指令与元素成功绑定时调用。
                                    (2).inserted:指令所在元素被插入页面时调用。
                                    (3).update:指令所在模板结构被重新解析时调用。

                        三、备注:
                                    1.指令定义时不加v-,但使用时要加v-;
                                    2.指令名如果是多个单词,要使用kebab-case命名方式,不要用camelCase命名。
        -->
        <!-- 准备好一个容器-->
        <div id="root">
            <h2>{{name}}</h2>
            <h2>当前的n值是:<span v-text="n"></span> </h2>
            <!-- <h2>放大10倍后的n值是:<span v-big-number="n"></span> </h2> -->
            <h2>放大10倍后的n值是:<span v-big="n"></span> </h2>
            <button @click="n++">点我n+1</button>
            <hr/>
            <input type="text" v-fbind:value="n">
        </div>
    </body>
   
    <script type="text/javascript">
        Vue.config.productionTip = false

        //定义全局指令
        /* Vue.directive('fbind',{
            //指令与元素成功绑定时(一上来)
            bind(element,binding){
                element.value = binding.value
            },
            //指令所在元素被插入页面时
            inserted(element,binding){
                element.focus()
            },
            //指令所在的模板被重新解析时
            update(element,binding){
                element.value = binding.value
            }
        }) */

        new Vue({
            el:'#root',
            data:{
                name:'尚硅谷',
                n:1
            },
            directives:{
                //big函数何时会被调用?1.指令与元素成功绑定时(一上来)。2.指令所在的模板被重新解析时。
                /* 'big-number'(element,binding){
                    // console.log('big')
                    element.innerText = binding.value * 10
                }, */
                big(element,binding){
                    console.log('big',this) //注意此处的this是window
                    // console.log('big')
                    element.innerText = binding.value * 10
                },
                fbind:{
                    //指令与元素成功绑定时(一上来)
                    bind(element,binding){
                        element.value = binding.value
                    },
                    //指令所在元素被插入页面时
                    inserted(element,binding){
                        element.focus()
                    },
                    //指令所在的模板被重新解析时
                    update(element,binding){
                        element.value = binding.value
                    }
                }
            }
        })
        
    </script>
</html>

二、回顾一个DOM操作

<!DOCTYPE html>
<html>
    <head>
        <meta charset="UTF-8" />
        <title>Document</title>
        <style>
            .demo{
                background-color: orange;
            }
        </style>
    </head>
    <body>
        <button id="btn">点我创建一个输入框</button>
       
        <script type="text/javascript" >
            const btn = document.getElementById('btn')
            btn.onclick = ()=>{
                const input = document.createElement('input')

                input.className = 'demo'
                input.value = 99
                input.onclick = ()=>{alert(1)}
                
                document.body.appendChild(input)

                input.focus()
                // input.parentElement.style.backgroundColor = 'skyblue'
                console.log(input.parentElement)
                
            }
        </script>
    </body>
</html>