How to use the tsx REPL to explore your ES2022 models

Open a new shell, and install the following dependencies:

$ npm i -D tsx dotenv @esbuild-kit/esm-loader`
$ npm i -S mongoose

Configure tsconfig.json

Set the following in your tsconfig.json:

  "compilerOptions": {
    "allowUnreachableCode": true,
    "allowJs": true,
    "baseUrl": ".",
    "checkJs": true,
    "esModuleInterop": true,
    "forceConsistentCasingInFileNames": true,
    "lib": ["ES2022"],
    "module": "ES2022",
    "moduleResolution": "NodeNext",
    "noImplicitAny": true,
    "outDir": "dist",
    "paths": {
      "*": ["node_modules/*", "*"]
    "rootDir": ".",
    "skipLibCheck": true,
    "sourceMap": true,
    "strict": true,
    "strictNullChecks": true,
    "target": "ES2022",
    "typeRoots": ["./node_modules/@types"],
    "types": ["node", "mocha"],
    "useUnknownInCatchVariables": false // TypeScript 4.4+ only!
  "include": ["./**/*.ts"],
  "exclude": ["node_modules", "<node_internals>/**", "./dist/**/*"]

tsx REPL

Now, you're ready to start the tsx REPL. Open a shell and type the following:

$ npx tsx --loader @esbuild-kit/esm-loader

And now you should see a > indicating that you are in the tsx REPL.

Use dotenv to load up a configuration file into a variable

Continuing in the REPL:

Let's say some of your configuration lives in a file in the root level directory named .env.development. This will hold environmental variables that are used in a configuration:


I've created a script that will set up a mongoose connection. It also puts all of your environment variables on process.env. Save the following in a file named config.ts in a directory named scripts under your root directory.

import dotenv from 'dotenv';
import mongoose from 'mongoose';
Promise = require('bluebird');
import User from '../app/models/user.model.js';

const config = dotenv.config({ path: './.env.development' });
mongoose.Promise = Promise;
mongoose.connect('mongodb://', {
  socketTimeoutMS: 0,
  authSource: process.env.AUTH_SOURCE,
  user: process.env.PWS_USER,
  pass: process.env.PWS_PASS,

export default config;
export { User };

Then open a tsx REPL to use it:

> const config = require('../server/scripts/config.ts');
> const newUser = new config.User({ firstName: 'Michaux', lastName: 'Kelley' });
> await newUser.save();
> const user = await config.User.find({ firstName: 'Michaux' });

Now for some real fun with mongoose models:

Type config.User followed by a dot ., and then press tab to see what's available to you. Like so:


And that's all there is to importing some configuration, connecting to mongoose, and exploring your models with the tsx REPL.

For further reading: