Exemplo de módulo que chama Vue Components.

carrinho.js

var carrinho = (function () {

    Vue.component('carrinho-item', {
      props: ['thumbnail', 'preco'],
      template: `
          <li class="carrinho-item">
              <figure class="carrinho-thumb">
                <img :src="thumbnail">
              </figure>
              <a class="carrinho-title" href="#"><slot></slot></a>
              <span class="preco">{{ '$' + preco }}</span>
          </li>
      `
    });

    Vue.component('Carrinho', {
        template: `
            <div class="carrinho navbar-dropdown">
                <div class="carrinho-content">
                    <ul class="carrinho-items">
                        <slot></slot>
                    </ul>
                    <button class="button is-success is-light carrinho-checkout">Finalizar compra</button>
                </div>
            </div>
        `
    });
    
});

export default carrinho;

index.js

import Carrinho from './carrinho.js';

Carrinho(); //Chama os componentes descritos no arquivo acima.

new Vue({
    el: "#root"
});