Mastering NestJS REPL: Unlocking New Ways to Interact with Your Application

Unlocking the Power of NestJS REPL

The NestJS REPL (Read-Eval-Print Loop) environment is a powerful tool that allows developers to interact with their applications from the command line. Introduced in NestJS 9, this feature is a game-changer for developers who want to inspect their application’s dependency graph, invoke methods on providers and controllers, and more.

Getting Started with NestJS REPL

To start using the NestJS REPL environment, you’ll need to set it up and configure it for your project. Here’s a step-by-step guide to get you started:

1. Create a new file called repl.ts in the same directory as your main.ts file.
2. Copy and paste the following code into the repl.ts file:
   “`typescript
   import { NestFactory } from ‘@nestjs/core’;
   import { AppModule } from ‘./app.module’;

async function bootstrap() {
const app = await NestFactory.create(AppModule);
await app.listen(3000);
}

bootstrap();
“
3. Run the commandts-node repl.ts` to launch the NestJS REPL environment.

Native Functions in NestJS REPL

The NestJS REPL environment comes with several native functions that make it easy to interact with your application. Here are some of the most useful ones:

• get: Retrieves an instance of a controller or injectable.
• debug: Prints a list of all registered modules, controllers, and providers.
• resolve: Resolves transient instances of controllers or injectables.
• select: Navigates the module tree and selects a specific module.

Using the Node REPL Environment

The NestJS REPL environment is built on top of the Node REPL environment, which means you can access all the features of the Node REPL environment from within the NestJS REPL. Here are some features you can use:

• .save: Saves evaluated commands to a file.
• .load: Loads JavaScript files into the current REPL session.
• .editor: Enters editor mode, allowing you to execute multiple lines of code.
• _: Accesses the result of the last operation.

Tips and Tricks

Here are some tips and tricks to help you get the most out of the NestJS REPL environment:

• Use the help function to get a list of available commands and their descriptions.
• Use the debug function to print a list of all registered modules, controllers, and providers.
• Use the select function to navigate the module tree and select a specific module.
• Use the _ variable to access the result of the last operation.

By mastering the NestJS REPL environment, you’ll be able to interact with your application in a whole new way, making it easier to debug, test, and develop your application.