how change the a.selector background style

section.vue

<template lang="pug>
section(id="main")
  a(href="#" @click="ModalShow" class="selector")
    span
     i(class="fa fa-bar-chart")
    span Open section modal
  <modal v-if="sectionModal">
    h1 hello my friend!!
    button(class="button is-info is-large modal-button" @click="closeModal") Close
  </modal>
</template>
<script>
import Jwtdecode from 'jwt-decode'
import Modal from 'layout/modal/BaseModal.vue'
export default {
  data: function() {
    return {
      sectionModal: false,
    }
  },
  components: {
    'modal': Modal,
  },
  methods: {
    ModalShow() {
      this.sectionModal = true;
    },
    closeModal() {
      this.sectionModal = false;
    }
  },
  mounted(){
    this.user = JwtDecode(localStorage.getItem('token'))
    if(!this.sectionModal){
      return document.querySelector('selector').style.backgroudColor = 'red';
    }
  }
}
</script>