< html > 
 < head > 
 < title > test < / title > 
 < script src= " https://cdn.jsdelivr.net/npm/.;></script>
width: 100px;
height: 100px;
background-color: red;} 
 .v-enter {
width: 0} 
 .v-enter-to {
width: 100px} 
 .v-enter-active {
transition: all 1s;} 
 .v-leave {
width: 100px} 
 .v-leave-to {
width: 0} 
 .v-leave-active {
transition: all 1s;} 
 < / style > 
 < / head > 
 < body > 
 < div id= "app" > 
 < button @ click=" change" > 21 < / button > 
 < transition > 
 < div id= "div" v show =" show" > < / div > 
 < / transition > 
 < / div > 
 < / body > 
 < script > 
 new Vue ({
el: "-sharpapp",
data:{
    show: true,
},
methods:{
    change() {
        this.show=!this.show;
    }
}}) 
 < / script > 
< / html > vue transition is not valid for width and height is not bug request the correct posture! Thank you ~

