import-single-ts

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Description

Drop-in replacement for the JS-native import(..) but **works with TypeScript
files**.

Use-case

1. You have a running node.js process, and you want to import .ts file from
it
2. BUT you realize you can't do import './myfile.ts',
require('./myfile.ts') or await import('./myfile.ts').
3. And you DON'T want an additional compilation step before the process
starts

This is where import-single-ts comes in. It allows you do
await importSingleTs('./myfile.ts') with _no extra steps needed_.

A common example would be defining things like configuration or setup in a
type-safe (_ts_) environment. Think vite.config.ts, webpack.config.ts, etc.

Usage

1. Make sure you've installed the esbuild (_it's a peer dependency_)
2. ``ts
import { importSingleTs } from 'import-single-ts';
// or for cjs: const { importSingleTs } = require('import-single-ts');
// ...
await importSingleTs('./some.ts'); // place where you need it
`

It has the same API as the native dynamic import — import()\*.

\* With some optional extras (_see below_).

Features & Limitations

- 🔄 Drop-in replacement for import() — no learning curve, you can just
replace the dynamic await import('./some.js') calls with
await importSingleTs('./some.ts') and it will just work as expected.
- ⚡ Fast — uses esbuild internally and learns from the best (_vite's &
esbuild plugins' source code_)
- 📐 Only compiles the minimum — The .ts file being loaded may have
multiple imports, which can, in turn, have more imports at any depth. Any
imported files, which node can run by itself, are not compiled. Instead,
they are loaded from their original path which means they are kept in the
internal node module cache and there won't be duplicate module executions if
they are imported again.
- 🚀 No dependencies + 1 peer dependency of esbuild
- 🧩️ Customizable import resolution — it exposes
options used in esbuild,
so you can provide things like
custom conditions
for
conditional exports,
aliases, etc. Simply pass in a second argument like so:
`ts
await importSingleTs('./some.ts', { conditions: ['mycompany-dev'], alias: { a: "b" }, ... })
`
- 💻️ Node.js REPL is supported as well
- ⛔️ Not intended for bun —
TypeScript is supported out of the box in bun, no need to use this package.
- ⛔️ Not intended for Windows — it's not tested on Windows and I won't be
able to dedicate extra time to debug problems there.

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consider becoming a sponsor.

Inspiration

- I wanted to load up the exports from .ts file and use it as a type-safe
config. There didn't seem to be an easy way to do that.
- I looked into
vite's
internal logic that deals with loading up vite.config.ts file. Before
settling on using esbuild I wasn't sure if there was a better way to do
compile on-the-fly. When I saw vite's approach I was relieved that looks like
the only way, and I've also adapted pieces of their config handling code
- I also researched
esbuild node-resolve plugin.
This was helpful to quickly glance esbuild plugin system. Sadly this relies
on the resolve package which
doesn't support package.json "exports" at all.
- I noticed that
node require.extensions is deprecated.
They actually recommend compiling ahead of time which is what this package
does.

Prior art

- ts-import — it internally uses
tsc, so loading up a file is _slow_. Another problem of tsc is it can
run only for a single project, so if you are in a monorepo environment, and
you depend on typescript files from other projects it won't work as expected.

Development notes

- It's build as cjs but can be used in both CJS and ESM environments.
That's because in mjs can't use stack trace to figure out the directory
where importSingleTs` was called from:
https://github.com/nodejs/node/issues/46992