Popup.vue

<template>
  <button @click="open = true"> Open Popup </button>
  <div class="popup" v-if='open'>
    <div class="popup-content" ref="popup">
      Lorem ipsum dolor sit amet consectetur adipisicing elit. Corporis aliquid autem reiciendis eius accusamus sequi, ipsam corrupti vel laboriosam necessitatibus sit natus vero sint ullam! Omnis commodi eos accusantium illum?
    </div>
  </div>
</template>

<script setup>
import { ref } from 'vue'
import { onClickOutside } from '@vueuse/core'

const open = ref(false) // state of our popup
const popup = ref() // template ref

// whenever our popup exists, and we click anything BUT it
onClickOutside(popup, () => {
  open.value  = false
})


</script>

<style scoped>
  button {
    border: none;
    outline: none;
    margin-right: 10px;
    background-color: #2ecc71;
    color: white;
    padding: 5px 10px;;
  }

  .popup {
    position: fixed;
    top: 0;
    left: 0;
    width: 100vw;
    height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    background: rgba(0, 0, 0, 0.1);
  }

  .popup-content {
    min-width: 300px;
    padding: 20px;
    width: 30%;
    background: #fff;
  }
</style>