<template>
  <div>
    <button @click="toggle">Toggle Box</button>
    <transition name="fade">
      <div v-if="isVisible" class="box"></div>
    </transition>
  </div>
</template>

<script>
export default {
  data() {
    return {
      isVisible: false
    };
  },
  methods: {
    toggle() {
      this.isVisible = !this.isVisible;
    }
  }
};
</script>

<style>
.fade-enter-active, .fade-leave-active {
  transition: opacity 0.5s;
}
.fade-enter, .fade-leave-to {
  opacity: 0;
}
.box {
  width: 100px;
  height: 100px;
  background-color: blue;
}
</style>

<template>
  <div>
    <button @click="toggle">Toggle Box</button>
    <transition @before-enter="beforeEnter" @enter="enter" @leave="leave">
      <div v-if="isVisible" class="box"></div>
    </transition>
  </div>
</template>

<script>
export default {
  data() {
    return {
      isVisible: false
    };
  },
  methods: {
    toggle() {
      this.isVisible = !this.isVisible;
    },
    beforeEnter(el) {
      el.style.opacity = 0;
    },
    enter(el, done) {
      setTimeout(() => {
        el.style.opacity = 1;
        done();
      }, 500);
    },
    leave(el, done) {
      setTimeout(() => {
        el.style.opacity = 0;
        done();
      }, 500);
    }
  }
};
</script>

<style>
.box {
  width: 100px;
  height: 100px;
  background-color: red;
}
</style>

<template>
  <div>
    <button @click="addItem">Add Item</button>
    <transition-group name="list" tag="ul">
      <li v-for="(item, index) in items" :key="item" class="list-item">
        {{ item }}
        <button @click="removeItem(index)">Remove</button>
      </li>
    </transition-group>
  </div>
</template>

<script>
export default {
  data() {
    return {
      items: []
    };
  },
  methods: {
    addItem() {
      this.items.push(`Item ${this.items.length + 1}`);
    },
    removeItem(index) {
      this.items.splice(index, 1);
    }
  }
};
</script>

<style>
.list-enter-active, .list-leave-active {
  transition: all 0.5s;
}
.list-enter, .list-leave-to {
  opacity: 0;
  transform: translateY(20px);
}
.list-item {
  margin: 10px 0;
  padding: 10px;
  background-color: lightgray;
  border: 1px solid #ccc;
}
</style>

npm install animate.css

<template>
  <div>
    <button @click="toggle">Toggle Box</button>
    <transition name="animated" enter-active-class="animate__animated animate__fadeIn" leave-active-class="animate__animated animate__fadeOut">
      <div v-if="isVisible" class="box"></div>
    </transition>
  </div>
</template>

<script>
import 'animate.css';

export default {
  data() {
    return {
      isVisible: false
    };
  },
  methods: {
    toggle() {
      this.isVisible = !this.isVisible;
    }
  }
};
</script>

<style>
.box {
  width: 100px;
  height: 100px;
  background-color: green;
}
</style>