with-custom-loader

with-custom-loader provides a minimal Node custom loader registration mechanism for importing files through a user-defined loader function.

import text from "./fixtures/text.txt" with { loader: "text" }

Overview

This package lets you register a loader by name and then import files with the with { loader: "<name>" } syntax in ESM.

You must enable loader by importing this module in your command:

node --import "with-custom-loader" ...

Next, you could register your loader to match your with attributes:

registerLoader(name: string, loaderFn: LoaderFn)

The registerer function receives a LoaderInput object with:

• source: the raw file contents as a string
• path: the original file path

The loader must return any value that becomes the module's default export.

Example

A loader that splits a text file into lines:

import { registerLoader, type LoaderFn } from "with-custom-loader"

export const txtLoader: LoaderFn = (input) => {
  return input.source.split("\n")
}

registerLoader("text", txtLoader)

Then import a .txt fixture using the loader:

import text from "./fixtures/text.txt" with { loader: "text" }

In this example, the imported text value is an array of strings.

Notes

• The loader registration happens through src/register.ts when the package is imported.
• The implementation reads the file from disk, applies the registered loader, and returns a module with the loader result as the default export.