deploying vueJs app on Azure Web App
When you use Vue.js on production or test (non-development) you should run build.
npm run build
After build, webpack extract all files and folders as "deployable" version of your application in "dist" folder in your root.
When you use files in "dist" directory, you wont need any kind of npm or webpack dependency.
If you really need webpack or development on your azure server, you might try install webpack globally.
npm install webpack@3.6.0 -g