REPL

Immersive provides a repl command:

repl

In repl mode, you have access to the same context as a command. It means that your helpers are available globally. See Enhanced context for more information.

Immersive REPL also supports top-level await & automatically resolves promises.

Example

matthieu:development > repl
> await db.get(1);
{
  id: 1,
  name: 'John Doe on development',
  status: 'VALIDATED',
  stars: 5
}
>

In this example, the await keyword is not required as if your command returns a promise it will be automatically resolved.

matthieu:development > repl
> db.get(1);
{
  id: 1,
  name: 'John Doe on development',
  status: 'VALIDATED',
  stars: 5
}
>

Make your own REPL

REPLs are great when you want to run several commands without losing context between them, when you just want to run quickly a couple of commands or when writing a script isn't worth it.

Immersive provides a convenient REPL command but also a REPL module that you can use if you need more flexibility and to create your own REPL.

Using the REPL module, you can provide a custom evaluation function. For example, you could make a REPL which runs queries against your database without leaving your CLI.

Let's see how we could do that:

// Import the repl module from Immersive
import { repl } from 'immersive';

// Create a Immersive command like you're used to
export const command = 'query';
export const description = 'Query database';

// Call repl in your action with the context provided by Immersive & your custom evaluation function
export const action = context => repl(context, evalQuery)

async function evalQuery(cmd, context, filename, callback) {
  // Immersive context
  const { logger, db } = context;
  // The query entered in the REPL
  const query = cmd.trim();
  // In this example we only support SELECT queries
  if (!query.toLowerCase().startsWith('select')) {
    logger.error('Only select queries are supported');
    callback(null);
    return;
  }
  // Query your database
  const rows = await db.runQuery(query);
  logger.info(`${rows.length} rows found`);
  // Display the results
  logger.table({ rows, name: 'Results' });
  // Don't forget to call the callback to be able to enter another query in the REPL
  callback(null);
}