Transpile

Basic Usage

zntc input.ts              # Output to stdout
zntc input.ts -o output.js # Output to file
zntc src/ --outdir dist/   # Recursive directory transpile
echo "const x: number = 1" | zntc -  # stdin input

Supported Transforms

TypeScript

• Type annotation removal
• Interface/type declaration removal
• Enum to object + IIFE conversion
• Namespace conversion
• as / satisfies expressions

JSX

# Classic (React.createElement)
zntc --jsx=classic app.tsx

# Automatic (react/jsx-runtime)
zntc --jsx=automatic app.tsx

# Development mode (jsxDEV + source info)
zntc --jsx=automatic-dev app.tsx

# Custom factory
zntc --jsx-factory=h --jsx-fragment=Fragment app.tsx

Decorators

# Legacy (experimentalDecorators)
zntc --experimental-decorators app.ts

# Move class fields to constructor
zntc --use-define-for-class-fields=false app.ts

Flow

# Automatic @flow pragma detection
zntc --flow app.js

Import attributes (ES2024)

with { type: "json" } is preserved as a round-trip across every import/export form. Legacy assert on static imports is auto-migrated to with (Node 20+ deprecates assert).

// static
import data from "./data.json" with { type: "json" };

// dynamic — the second argument is preserved too
const mod = await import("./data.json", { with: { type: "json" } });

// re-export
export { default as data } from "./data.json" with { type: "json" };
export * from "./data.json" with { type: "json" };
export * as ns from "./data.json" with { type: "json" };

Local JSON imports are already inlined during bundling based on extension. with { type } matters when the bundle output runs on Node as ESM, or when emitting sources that require spec-compliant JSON module syntax.

Behavior: with { type } is round-trip metadata. Loader selection is purely extension-based — attrs will not force a loader (.txt → JSON) nor error on unknown type values.

Output Options

Module Format

zntc --format=esm app.ts   # ESM (default)
zntc --format=cjs app.ts   # CommonJS
zntc --format=iife app.ts  # Immediately Invoked Function Expression
zntc --format=umd app.ts   # UMD (browser + Node)
zntc --format=amd app.ts   # AMD (RequireJS)

ES Target / Engine Target

# ES version target — es2015 ~ esnext
zntc --target=es2020 app.ts

# Engine version target — feature-level downleveling
zntc --target=chrome80,safari14 app.ts
zntc --target=node18 app.ts
zntc --target=hermes0.70 app.ts   # React Native (Hermes)

Engine targets only emit the transformations required by each engine’s compatibility table.

Minify

zntc --minify app.ts  # All three

# Granular (esbuild-compatible)
zntc --minify-whitespace app.ts    # Whitespace/semicolons/newlines (debuggable)
zntc --minify-syntax app.ts        # true→!0, paren removal, constant folding, drop unreferenced class expression names
zntc --minify-identifiers app.ts   # Shorten local identifiers

Combine flags freely — e.g. enable only --minify-whitespace for dev builds to get a debuggable, smaller output.

Source Maps

zntc --sourcemap app.ts -o app.js
# Generates app.js + app.js.map

Quote Style

zntc --quotes=single app.ts   # Single quotes
zntc --quotes=double app.ts   # Double quotes (default)
zntc --quotes=preserve app.ts # Preserve original

ASCII Only

zntc --ascii-only app.ts  # Escape non-ASCII to \uXXXX

Define

zntc --define:DEBUG=false --define:VERSION='"1.0.0"' app.ts

Values must be JavaScript literals. Watch out for missing quotes.

# ✗ Wrong — admin becomes an identifier, producing unintended code
zntc --define:USERNAME=admin app.ts

# ✓ Right — quote it so it becomes a string literal
zntc --define:USERNAME='"admin"' app.ts

# ✓ Numbers / booleans / null are literals as-is
zntc --define:DEBUG=false --define:MAX=100 --define:USER=null app.ts

# ✓ Object / array work too if they're valid JSON literals
zntc --define:ENV='{"mode":"prod"}' app.ts

Shell quoting gotcha: in bash/zsh you need to wrap the double quotes in single quotes to keep them.

Drop

Three independent removal options that can be combined.

# Remove console.* calls
zntc --drop=console app.ts

# Remove debugger statements
zntc --drop=debugger app.ts

# Remove labeled blocks entirely — comma-separated labels
zntc --drop-labels=DEV,TEST app.ts

# All three at once
zntc --drop=console --drop=debugger --drop-labels=DEV,TEST app.ts

--drop-labels example:

// Source
DEV: {
  console.log("debug only");
  attachDevtools();
}

// --drop-labels=DEV → the whole block disappears in the output

Wrap dev-only debug code in a label and you can strip it all in one switch for production builds.