I am working on Angular application using bootstrap 4.
I need help related to scss adding in my angular application.
My question is:
i.e.
npm install bootstrap --save  
And, open angular.json file and add bootstrap file path to the styles section. Like:
"styles": [
  "src/styles.css",
  "node_modules/bootstrap/dist/css/bootstrap.min.css"
],
Is the above way is same for both the version of angular.
You need to do the following:
Add Bootstrap to package.json (which is done with npm install bootstrap --save)
Add Bootstrap to angular.json (jQuery is required too)
  "styles": [
     "styles.css".
     "../node_modules/bootstrap/dist/css/bootstrap.min.css"
  ],
  "scripts": [
     "../node_modules/jquery/dist/jquery.min.js",
     "../node_modules/popper.js/dist/umd/popper.min.js",
     "../node_modules/bootstrap/dist/js/bootstrap.min.js"
  ],
Reference Bootstrap in the Angular app (app.module.ts)
import bootstrap from "bootstrap";
Demo: https://codesandbox.io/s/kmm2q7zvko
Article: https://medium.com/wdstack/angular-7-bootstrap-4-starter-25573dff23f6
OPTION-1
execute
npm install bootstrap@4 jquery --save
The JavaScript parts of Bootstrap are dependent on jQuery. So you need the jQuery JavaScript library file too.
"styles": [
    "src/styles.css","node_modules/bootstrap/dist/css/bootstrap.min.css"
],
"scripts": [
    "node_modules/jquery/dist/jquery.min.js",
    "node_modules/bootstrap/dist/js/bootstrap.min.js"
]
OPTION-2
ng-bootstrap It contains a set of native Angular directives based on Bootstrap’s 
    markup and CSS. As a result, it's not dependent on jQuery or Bootstrap’s JavaScript
npm install --save @ng-bootstrap/ng-bootstrap
After Installation import it in your root module and register it in @NgModule imports` array
import {NgbModule} from '@ng-bootstrap/ng-bootstrap';
@NgModule({
    declarations: [AppComponent, ...],
    imports: [NgbModule.forRoot(), ...],
    bootstrap: [AppComponent]
})
ng-bootstrap requires Bootstrap's 4 css to be added in your project. you need to 
    Install it explicitly via:
npm install bootstrap@4  --save 
In your angular.json add the file paths to the styles array in under build target
"styles": [
    "src/styles.css",
    "node_modules/bootstrap/dist/css/bootstrap.min.css"
],
                        Bootstrap not working properly in Angular 6 / 7 / 8
I tried most of the solution over web nothing work for me
Only below code work for me
No need to change in angular.json
Directly add below line into style.css file
@import "../node_modules/bootstrap/dist/css/bootstrap.css"
because in angular.json already we are providing reference of style.css
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