Была ли такая же проблема изменилась моя зависимость в package.json из этого
"dependencies": {
"@angular/animations": "^5.0.0",
"@angular/common": "^5.0.0",
"@angular/compiler": "^5.0.0",
"@angular/core": "^5.0.0",
"@angular/forms": "^5.0.0",
"@angular/http": "^5.0.0",
"@angular/platform-browser": "^5.0.0",
"@angular/platform-browser-dynamic": "^5.0.0",
"@angular/router": "^5.0.0",
"@ng-bootstrap/ng-bootstrap": "^1.0.0-beta.9",
"bootstrap": "^4.0.0-beta.3",
"core-js": "^2.4.1",
"font-awesome": "^4.7.0",
"zone.js": "^0.8.14"
}
(изменение «bootstrap»: «4.0.0-beta.2» до стабильной версии)
"dependencies": {
"@angular/animations": "^5.0.0",
"@angular/common": "^5.0.0",
"@angular/compiler": "^5.0.0",
"@angular/core": "^5.0.0",
"@angular/forms": "^5.0.0",
"@angular/http": "^5.0.0",
"@angular/platform-browser": "^5.0.0",
"@angular/platform-browser-dynamic": "^5.0.0",
"@angular/router": "^5.0.0",
"@ng-bootstrap/ng-bootstrap": "^1.0.0-beta.9",
"bootstrap": "4.0.0-beta.2",
"core-js": "^2.4.1",
"font-awesome": "^4.7.0",
"zone.js": "^0.8.14"
},
затем запустите: npm install ng serve
задача решена.!!