What are the types of injector hierarchies?

There are two types of injector hierarchies in Angular

1. ModuleInjector hierarchy: It configure on a module level using an @NgModule() or @Injectable() annotation.
2. ElementInjector hierarchy: It created implicitly at each DOM element. Also it is empty by default unless you configure it in the providers property on @Directive() or @Component().

Practical Code Example

// Injector Hierarchies:
// 1. EnvironmentInjector Hierarchy (Root, Platform, Null)
// 2. ElementInjector Hierarchy (Component DOM tree)