Smarter way to organize “import” statements using “index.ts” file(s) in Angular

“Module” is a tricky term. For Angular, Module is a container/package to hold various components, reference other Modules, provide Dependency Injection etc. Whereas for Typescript, “Component” and “Module” are essentially same thing to transpile — JavaScript Module.

Angular components and modules are written in Typescript files as a module using export keyword. As we build our Angular application to the greater extend, we end up creating many feature modules and components. We can refer a component or a module in other using “import” statement. Without “import” Typescript compiler shall throw exception for unknown type.

Consider a simple application with Login, SignUp, Dashboard, Product, Cart and Account feature. This application is routed using simple Angular routing strategy. Here is the route configuration and route graph:

Since we are using many components in app.routing.module.ts file, we must import their reference for .component.ts and .module.ts files. A general import statements would looks like this:

Even though VS Code and other smart editors resolve path for component and module still these import statements looks lengthy and cumbersome isn’t it?

Another pain point is, if we change folder structure then we must change all import statements to reflect correct path.

You may have observed import statement used for importing packages from @angular library. We can import more than one component, module from same import statement even though they are in different .ts files.

This is possible because of index.ts file.

Typescript module resolution picks up index.ts file from folder name if it is there and try to import packages.

In this file, we can export all folder specific components and modules. For example, consider index.ts file inside products folder:

Now, in app.routing.module.ts file, we can import all these components and module with a single statement as below.

If you notice, we are importing components and module from ./dashboard/products. Yes, we are specifying each component or module name neither we are providing index.ts file.

Here are the complete import statement using index.ts file approach

Looks neat and simple, isn’t it?

Generally you should create index.ts file in feature specific folders. But it is up to you how many index.ts file should be created, should it be feature specific, component specific etc. This decision shall vary per application, per developer and problem statement.

Here is the GitHub repository without use of index.ts files

And here is the GitHub repository which uses index.ts files for organizing import statements.


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