bootstrap 4 for styles.css in angular code example
Example 1: adding bootstrap to angular
$ npm install --save bootstrap
Example 2: installing bootstrap in angular 9
.... "styles": [ "node_modules/bootstrap/dist/css/bootstrap.min.css", "src/styles.css" ], "scripts": [ "node_modules/jquery/dist/jquery.min.js", "node_modules/bootstrap/dist/js/bootstrap.min.js" ].....