Global Variable Replacement

Oxc transformer supports replacing global variables.

Define

"Define" feature provides a way to replace global variables with constant expressions. This feature is similar to esbuild's define option.

// input
const foo = __DEV__ ? 1 : 2;

// output
const foo = 1;

// Example
import { transform } from "oxc-transform";

const result = transform("lib.js", sourceCode, {
  define: {
    __DEV__: "true",
  },
});

Each define entry maps an expression to a string of code containing an expression. The keys of it must be an identifier (e.g. __DEV__), or a dotted sequence of identifiers (e.g. process.env.NODE_ENV, import.meta.env.MODE). The values of it must be a valid expression.

Always quote the values

The values of define are the string of expressions. This means the value should always a string. If you mean a string literal, you should quote it (e.g. __MODE__: '"development"', __MODE__: JSON.stringify("development")).

The object reference are not shared

Differently from esbuild, when passing an object to the value of the define option, the object reference is not shared. This means that if you change the object, the changes will not be reflected in the other places.

const foo = __OBJECT__;
foo.bar = 1;
console.log(foo.bar); // 1

const bar = __OBJECT__;
console.log(foo.bar); // undefined

// Example
import { transform } from "oxc-transform";

const result = transform("lib.js", sourceCode, {
  define: {
    __OBJECT__: "{}",
  },
});

Inject

"Inject" feature provides a way to replace global variables with an import from a module. This feature is similar to esbuild's inject option and @rollup/plugin-inject.

// input
const foo = new Promise((resolve) => resolve(1));

// output
import { Promise as P } from "es6-promise";
const foo = new P((resolve) => resolve(1));

// Example
import { transform } from "oxc-transform";

const result = transform("lib.js", sourceCode, {
  inject: {
    P: ["es6-promise", "Promise"],
  },
});

Each inject entry maps an expression to an imported identifier. The keys of it must be an identifier (e.g. __DEV__), or a dotted sequence of identifiers (e.g. process.env.NODE_ENV). The values of it must be a string of the import source, or a tuple of strings of the import source and the import name (* is namespace import).

const examples = {
  // import { Promise } from 'es6-promise'
  Promise: ["es6-promise", "Promise"],
  // import { Promise as P } from 'es6-promise'
  P: ["es6-promise", "Promise"],
  // import $ from 'jquery'
  $: "jquery",
  // import * as fs from 'fs'
  fs: ["fs", "*"],
  // use a local module instead of a third-party one
  "Object.assign": path.resolve("src/helpers/object-assign.js"),
};