Module not found: Can't resolve 'core-js/modules/es.array.concat' code example
Example 1: Module not found: Error: Can't resolve 'core-js/modules/es6.object.create
solution install core-js@2.6.5
Example 2: Module not found: Error: Can't resolve 'core-js/es7/reflect'
// Change import in polyfills.ts
import 'core-js/es7/reflect';
// for
import 'core-js/es/reflect';