How to hide the elements in the template in vue?

Why is the value changed and v-if is not triggered?
clipboard.png

</button></td>
                </tr></table>`,
            methods:{
                addInput:function(id){
                    this.isInput1 = true;
                    this.isSpan1 = false;
                    console.log(id);
                    
                },
                addSpan:function(e){
                    alert(1);
                },
                showMsg:function(items){
                    console.log(items.name+":"+items.age)
                }
            }
        });

        var vm = new Vue({
            el:"-sharpbox",
            data:{
                title:["","","",""],
                arr:[
                    {name:"",age:"12",habit:"ok",id:"J0002"},
                    {name:"",age:"14",habit:"o12k",id:"J0003"},
                    {name:"",age:"24",habit:"aksjdkas",id:"J0004"}
                ],
                itemId:5,
            }
        })
Mar.30,2021

v-once renders elements and components only once. Data changes will not be rendered


the subject must not find that he has added VLineX, hehe

MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1bee537-5484a.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1bee537-5484a.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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