External class in Vue

index.vue

// Question: How can I extract the "DataTransformer" class and reference it back here?
// Solved!!!
<script>

// extract this in <root>/src/helpers/helper.js (or anywhere you want it)
export class DataTransformer {
    static transform(data) {
        const transformedData = {};
        ....
        return transformedData
    }
}

// and import it like this
import { DataTransformer } from '@/helpers/helper.js';

 export default {
     name: 'hello',
     data() {
          return {
              world: {}
          }
     },
     methods: {
        getUsers() {
            ....
            .then(
                (res) => {
                    this.world = DataTransformer.transform(response.data)
                }
            );
        }
     }
 }
</script>