Start new project:
vue create project-name
".env" fiiles help to declare global variable name available to access everywhere inside the project.
".env" file works globally if ".env.development" file is not present; otherwise it works for production environment.
Vue can only access the files if it starts with "VUE_APP_" prefix. For example from ".env" file "VUE_APP_API_URL" can be accessible with "process.env.VUE_APP_API_URL".
Using @vue/cli-service-global we can run a single independent component for rapid prototyping.
For installation run,
npm install -g @vue/cli-service-global
Then we can use vue serve FileName.vue to experiment with that component.