[Vuejs]-Error on Laravel after installing VueJS. Request failed with status 404

I think you need to run:

npm run watch

After adding VueJS to your project you need to install all dependencies by executing:

npm install

Then you can either compile your assets onetime by executing:

npm run dev

Or start a watcher which compiles your assets automatically after detecting a filechange:

npm run watch

The compile process will generate the app.js file which is missing in your case. You can read more about this process or possibilities in laravel here (laravel docs about frontend).

After pulling your project you need to install all dependencies using

npm i

Then you can build it for development one-time using

npm run dev

Or for real-time updates

npm run watch

And when your project is ready for production

npm run prod