Middleware

This is a simple example that demonstrates how to register middleware that run before the command handler. Middleware can do a lot of things. Almost everything that middleware can do could be done at the beginning of the handler function, but middleware keeps the handler clean and focused on the command's behavior as well as being much more composable.

Some things middleware can do:

Modify the arguments object
Perform validation that takes multiple arguments into account
Perform side effects

Code

Middleware
import cliForge from 'cli-forge';

const cli = cliForge('basic-cli')
  // Requires a command to be provided
  .demandCommand()

  // Middleware registered on parent commands will be invoked before the child command's middleware
  .middleware(() => {
    console.log('ABOUT TO RUN A COMMAND');
  })

  // Registers "hello" command
  .command('hello', {
    // Builder is used to define the command's options
    builder: (args) =>
      args
        .option('name', {
          type: 'string',
          description: 'The name to say hello to',
          default: 'World',
        })
        // Middleware can mutate the args object
        .middleware((args) => {
          args.name = args.name.toUpperCase();
        })
        // Multiple middleware can be registered
        .middleware(() => {
          console.log('HELLO MIDDLEWARE');
        }),
    // Handler is used to define the command's behavior
    handler: (args) => {
      console.log(`Hello, ${args.name}!`);
    },
  });

// We export the CLI for a few reasons:
// - Testing
// - Composition (a CLI can be a subcommand of another CLI)
// - Docs generation
export default cli;

// Calling `.forge()` executes the CLI. It's single parameter is the CLI args
// and they default to `process.argv.slice(2)`.
if (require.main === module) {
  (async () => {
    await cli.forge();
  })();
}

View on TypeScript Playground

Usage

node ./middleware.js hello --name sir

These examples are ran as e2e tests on pull-requests and releases to verify they are accurate and up to date. If you see any issues, please open an issue on the github repo.

Code​

Usage​

Code

Usage