JavaScript Toggle Dark mode

[Jonny Preis]

Hello im trying to get my Dark mode working but i cant find the problem

<template>
  <!--<v-btn @click="toggleTheme" text rounded outlined>Change Mode</v-btn>
    --><v-btn icon @click="toggleTheme"  v-on:keyup="emitToParent">
        
        <v-icon >
          {{ ($vuetify.theme.dark) ? 'mdi-weather-night' : 'mdi-weather-sunny' }}
        </v-icon>
      </v-btn>
</template>

<script>
export default {
   data() {
    return {
      dark: null,
      darkmode: null,
    }
  },
  methods: {
    toggleTheme() {
      if(this.darkmode[0].force){
        this.dark = true;
        this.emitToParent();
        this.$vuetify.theme.dark = true;
        localStorage.setItem("dark_mode", this.$vuetify.theme.dark.toString());

      }else{
        this.$vuetify.theme.dark =false;
        localStorage.setItem("dark_mode", this.$vuetify.theme.dark.toString());
        this.dark = this.$vuetify.theme.dark;
        this.emitToParent();
        //console.log(this.$vuetify.theme.dark);
      }
      
    },
     emitToParent () {
      this.$emit('childToParent', this.dark)
    },
    getData(){
      this.axios
      .post(this.$baseURL_Avancis + '/backend/sideDrawer.php')
      .then(response => (
          this.darkmode = response.data.darkmode,
          this.force()
          //,console.log(this.darkmode[0].force)
          
      
        ))
    },
  
    startup(){
      const theme = localStorage.getItem("dark_mode");
      
        if (theme) {
          if (theme == "true") {
            this.dark = true;
            this.emitToParent();
            this.$vuetify.theme.dark = true;
          } else {
            this.dark = false;
            this.emitToParent();
            this.$vuetify.theme.dark = false;
          }
        }
      
    }
    
  },
  mounted() {
        this.getData()
        this.startup()
        
        
    },
};
</script>

Maybe you can help me find the problem
ty