NGB's purpose in life is to be a complete replacement for Bootstrap's components that require JavaScript (such as the components listed at the beginning of the chapter). In fact, on the very first page of the Getting Started section on their official website, they go further and say that you shouldn't be using any JavaScript-based components at all—or even their dependencies, such as jQuery or Popper.js. This can be found at: https://ng-bootstrap.github.io/#/getting-started.