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dnt - Deno to Node Transform

deno doc

Prototype for a Deno to npm package build tool.

What does this do?

It takes a Deno module and creates an npm package for use on Node.

There are several steps done in a pipeline:

  1. Transforms Deno code to Node/canonical TypeScript including files found by deno test.
    • Rewrites module specifiers.
    • Injects a Deno shim for any Deno namespace usages.
    • Rewrites Skypack and ESM specifiers to a bare specifier and includes these dependencies in a package.json.
    • When remote modules cannot be resolved to an npm package, it downloads them and rewrites specifiers to make them local.
    • Allows mapping any specifier to an npm package.
  2. Type checks the output.
  3. Emits ESM, CommonJS, and TypeScript declaration files along with a package.json file.
  4. Runs the final output in Node through a test runner running all Deno.test calls. Deletes the test files when complete.


// ex. scripts/build_npm.ts
import { build } from "";

await build({
  entryPoints: ["./mod.ts"],
  outDir: "./npm",
  typeCheck: true,
  declaration: true,
  test: true,
  package: {
    // package.json properties
    name: "my-package",
    version: Deno.args[0],
    description: "My package.",
    license: "MIT",
    repository: {
      type: "git",
      url: "git+",
    bugs: {
      url: "",
  // optional specifier to npm package mappings
  mappings: {
    "": {
      name: "code-block-writer",
      version: "^10.1.1",
# run script
deno run --allow-read --allow-write --allow-net --allow-run scripts/build_npm.ts 0.1.0

# go to output directory and publish
cd npm
npm publish

Example Build Logs

[dnt] Transforming...
[dnt] Running npm install...
[dnt] Building project...
[dnt] Type checking...
[dnt] Emitting declaration files...
[dnt] Emitting ESM package...
[dnt] Emitting CommonJS package...
[dnt] Running tests...

> test
> node test_runner.js

Running tests in ./umd/mod.test.js...

test escapeForWithinString ... ok
test escapeChar ... ok

Running tests in ./esm/mod.test.js...

test escapeForWithinString ... ok
test escapeChar ... ok
[dnt] Complete!

JS API Example

For only the Deno to canonical TypeScript transform which may be useful for bundlers, use the following:

// docs:
import { transform } from "";

const outputResult = await transform({
  entryPoints: ["./mod.ts"],
  testEntryPoints: ["./mod.test.ts"],
  shimPackageName: "deno.ns",
  // mappings: {}, // optional specifier mappings

Rust API Example

use std::path::PathBuf;

use deno_node_transform::ModuleSpecifier;
use deno_node_transform::transform;
use deno_node_transform::TransformOptions;

let output_result = transform(TransformOptions {
  entry_points: vec![ModuleSpecifier::from_file_path(PathBuf::from("./mod.ts")).unwrap()],
  test_entry_points: vec![ModuleSpecifier::from_file_path(PathBuf::from("./mod.test.ts")).unwrap()],
  shim_package_name: "deno.ns".to_string(),
  loader: None, // use the default loader
  specifier_mappings: None,