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Export Conditions

Export conditions are a standard feature of Node package resolution. You can add custom conditions to your exports map, then enable them at runtime through your build tool.

Add a condition to your package​

Pick a condition name (for example local-dev) and add it as the first entry under each export. This ensures it wins when enabled.

{
  "exports": {
    ".": {
      "local-dev": "./src/index.ts",
      "import": {
        "types": "./dist/esm/index.d.ts",
        "default": "./dist/esm/index.js"
      },
      "require": {
        "types": "./dist/cjs/index.d.ts",
        "default": "./dist/cjs/index.cjs"
      }
    }
  }
}

Enable the condition at runtime​

The core package returns a list of conditions. Adapters then apply those conditions to your tool. For example, the Vite adapter injects them into resolve.conditions.

If the list is empty, no extra condition is enabled and your normal exports are used.

Picking a name​

  • Use a name that will never collide with standard Node conditions.
  • local-dev is a good default and is used in the examples.

Safety​

Export conditions do not change your published packages. They only change which files are chosen when a particular condition is enabled.