when I execute yarn mix in my project, i got this error:

ERROR in ./resources/js/app.js 1:0-22
Module not found: Error: Can't resolve './bootstrap' in '/Users/xxx/Sites/localhost/xxx/resources/js' 

The bootstrap folder exists. Does anyone know what's wrong?

App.js:

require('./bootstrap');

import Alpine from 'alpinejs';

window.Alpine = Alpine;

Alpine.start();