The problem of appear in vue

< div id= "app" >

    <transition
        appear
        enter-active-class="animated swing"    
        leave-active-class="animated shake"
        appear-class="animated swing"
        appear-to-class="animated shake"
        appear-active-class="animated shake"
    >
        <div v-if="show">hello world</div>
    </transition>
    <button @click="handleClick"></button>
</div>

the code written in this way (prerequisite: animate.css is referenced as a library), why does the transition effect of the dom node in the initial rendering not take effect?

Apr.17,2021
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