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We will walk through the steps to build a CLI application using TypeScript

By David Li on Fri, 4 April 2024

Building command-line interface (CLI) applications is an essential skill for developers, especially those who work on server-side applications. CLI applications offer a convenient way to interact with programs and automate repetitive tasks, making them a valuable tool for developers.

TypeScript is a superset of JavaScript that adds optional static typing and other features to the language. It provides a great way to build CLI applications, thanks to its strong typing, object-oriented programming features, and compile-time error checking.

In this article, we will walk through the steps to build a CLI application using TypeScript.

Step 1: Set up the project

The first step is to set up a TypeScript project using your preferred package manager. You can use npm or yarn to create a new project and install the necessary dependencies.

Once your project is set up, you can create a file called index.ts that will serve as the entry point for your CLI application.

Step 2: Define the CLI commands

Next, you need to define the commands that your CLI application will support. You can use a library like Commander.js or Yargs to define and parse command-line arguments.

Here is an example of defining a command using Commander.js:

import commander from 'commander';

commander
  .command('say-hello <name>')
  .description('Say hello to someone')
  .action((name: string) => {
    console.log(`Hello, ${name}!`);
  });

commander.parse(process.argv);

This code defines a command called “say-hello” that takes a required argument called “name”. When the command is executed, it will print a greeting to the console.

Step 3: Implement the CLI commands

Once you have defined your CLI commands, you need to implement the actions that will be executed when the commands are invoked.

Here is an example of implementing the “say-hello” command:

import commander from 'commander';

commander
  .command('say-hello <name>')
  .description('Say hello to someone')
  .action((name: string) => {
    console.log(`Hello, ${name}!`);
  });

commander.parse(process.argv);

This code defines a command called “say-hello” that takes a required argument called “name”. When the command is executed, it will print a greeting to the console.

Step 4: Compile and run the application

Finally, you need to compile your TypeScript code into JavaScript and run the application. You can use the TypeScript compiler (tsc) to compile your code, and then run the resulting JavaScript file using Node.js.

Here is an example of compiling and running the CLI application:

$ tsc index.ts
$ node index.js say-hello John
Hello, John!

This code compiles the TypeScript code into JavaScript and then runs the “say-hello” command with the argument “John”.

Conclusion

Building CLI applications using TypeScript is a great way to take advantage of the language’s features and build robust, scalable applications. With the help of a library like Commander.js or Yargs, you can define and parse command-line arguments, and then implement the actions that will be executed when the commands are invoked. By following these steps, you can build CLI applications that are easy to use, maintain, and extend.

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