vue.js – Auto rebuild Vue project

I am running my Vue.js project with npm run start command, where start script is:
“start”: “PORT=7200 node router.js”. The router.js usage is crucial here and has to stay, although it would be much easier with vue-cli-service serve…
Is there a possibility to configure an auto rebuild so that after any change it is reflected without npm run build all over again?

router.js:

const Router = require("@sap/approuter")

Router().start({
  extensions: [require("./extensions/router-extension")],
})