Bazel allows us to break an application into distinct build units. In Angular, build units are defined at the NgModule level. This means the scope of a build can be as granular as a single NgModule. If a change is internal to an NgModule, only that module needs to be rebuilt.Closure Compiler is a JavaScript optimizer written and used at Google. We compile most of our Angular apps with it, to produce the smallest JavaScript bundles.https://github.com/angular/closure-demo/wiki

Closure Compiler is a JavaScript optimizer written and used at Google. We compile most of our Angular apps with it, to produce the smallest JavaScript bundles. This is part of the "ABC" effort (Angular, Bazel, and Closure). Closure compiler is an advanced tool. Refer links 1) https://www.code-sample.com/2018/05/angular-6-7-bazel-compiler.html 2) https://medium.com/@Jakeherringbone/what-angular-is-doing-with-bazel-and-closure-21f526f64a34 3) https://codeburst.io/bazel-an-experimental-and-unofficial-feature-of-angular-6-946e880b4637