oxc-codegen

Fast, synchronous code generation for JavaScript and TypeScript ASTs.

oxc-codegen turns an ESTree or TS-ESTree AST into formatted source code. It supports JavaScript, JSX, TypeScript, and TSX.

The printer is a port of Oxc's Rust oxc_codegen crate. With the default options, both printers produce byte-identical output: tab indentation, double-quoted strings, and no comments.

Installation

npm install oxc-codegen

oxc-codegen is ESM-only and requires Node.js ^20.19.0 or >=22.12.0.

Quick start

Pair it with oxc-parser to parse and print source code:

import { printSync } from "oxc-codegen";
import { parseSync } from "oxc-parser";

const { program } = parseSync("input.js", "const answer=6*7");
const { code } = printSync(program);

console.log(code);
// const answer = 6 * 7;

You can also print a manually constructed AST:

const program = {
  type: "Program",
  sourceType: "script",
  body: [
    {
      type: "ExpressionStatement",
      expression: {
        type: "CallExpression",
        callee: {
          type: "MemberExpression",
          object: { type: "Identifier", name: "console" },
          property: { type: "Identifier", name: "log" },
          computed: false,
          optional: false,
        },
        arguments: [{ type: "Literal", value: "Hello!" }],
        optional: false,
      },
    },
  ],
};

console.log(printSync(program).code);
// console.log("Hello!");

TypeScript and TSX

Set ts when the AST can contain TypeScript nodes. For TSX, set both ts and jsx:

const { program } = parseSync("component.tsx", "const Box = <T,>(value: T) => <div>{value}</div>");

const { code } = printSync(program, {
  ts: true,
  jsx: true,
});

API

printSync(node, options?)

function printSync(
  node: ESTree.Program | ESTree.Statement,
  options?: Options,
): {
  code: string;
  map: SourceMap | null;
};

Prints a complete Program or a single statement and returns the generated source code, and (when requested) a standard Source Map v3 object.

import { printSync } from "oxc-codegen";
import { parseSync } from "oxc-parser";

const sourceText = "const answer=6*7";
const { program } = parseSync("input.js", sourceText);
const { code, map } = printSync(program, {
  sourcemap: true,
  sourceFilename: "input.js",
  sourceText,
});

Source-map mappings require sourceText and nodes with valid Oxc start / end offsets. A manually constructed AST without offsets can still be printed, but its source map has an empty mappings string.

Options

| Option | Type | Default | Description | | :-------------------- | :-------- | :------ | :--------------------------------------------------------------- | | indent | string | "\t" | Non-empty string of spaces and/or tabs used for one indent level | | startingIndentLevel | number | 0 | Starting indent level, from 0 to 1000 | | jsx | boolean | false | Enable TSX-safe printing for ambiguous TypeScript syntax | | ts | boolean | false | Select the printer that supports TypeScript nodes | | sourcemap | boolean | false | Return a Source Map v3 object in map | | sourceFilename | string | "" | Original source filename recorded in the source map | | sourceText | string | - | Original text required for source-map mappings and content |

Why pure JavaScript?

Most Oxc packages use native bindings. This package deliberately does not: when an AST already lives in JavaScript, passing the entire object graph across a JS/native boundary can cost more than printing it in place. oxc-codegen avoids that serialization and uses specialized printer builds for JavaScript and TypeScript workloads.

See DESIGN.md for the implementation details and performance constraints.

Current limitations

• Comments are not printed.
• Minified output is not supported.

Benchmarks

Representative time per printSync call:

| Fixture | Bytes | Time | | :--------------------------- | --------: | ---------: | | tiny.js | 26 | 0.0001 ms | | RadixUIAdoptionSection.jsx | 2,518 | 0.0070 ms | | react.development.js | 72,141 | 0.1518 ms | | binder.ts | 193,077 | 0.3364 ms | | App.tsx | 415,340 | 1.2912 ms | | lodash.js | 544,096 | 0.7977 ms | | kitchen-sink.tsx | 732,222 | 4.2924 ms | | antd.js | 6,683,633 | 16.9652 ms |

These figures come from one machine and are illustrative, not a regression baseline. Results vary between runs, most noticeably for large fixtures such as antd.js.