ludus-repl

A basic live-reloading repl

What

A node repl that live-reloads a given module (esm or cjs) and its dependencies, for a more interactive coding experience. It's not very sophisticated: it watches for changes only in node's process.cwd, so it's best to invoke it from the root of the project.

Installation

npm i @kredati/ludus-repl --save-dev

Use

npx repl ./src/foo  # starts a repl for ./src/foo.js

Context

This repl does not load your module as a script (i.e. using the .load command). Instead, it loads just what all is in the file in question's exports (esm [export {foo}] or cjs [module.exports = {foo}]). If you wish to expose local variables that are not exported to the repl, the repl also mounts a global variable, __contextualize, which adds local variables to the repl context. It takes a record (object literal), and puts everything in that record into context in the repl, using the keys in the object as variable names. In the repl, there is also a context variable, __context, which will show you what the repl has loaded.

Consider the following module:

const foo = 'foo'

const bar = () => foo

export {bar}

The repl will only load bar. If you wanted to also include foo in the repl context, you would add __contextualize({foo}). At which point, on saving the file, the new context would be

Known issues

The repl can handle errors when reloading the module it's working on, but it will fall over on uncaught errors in its dependencies. So if you're editing dependencies instead of the loaded file, be careful to avoid parsing errors.

Also, the repl works in a different realm than modules run in, so subtle (and not-so-subtle) errors around global variables can creep in. Be especially careful of prototype chains; use Array.isArray.