babel-preset-daun

Babel Preset

A default babel preset for my personal projects.

Transforms

Contains transforms for all stage 4 and stage 3 syntax. Stage 4 syntax that is excluded is as follows:

• generators: regenerator-runtime is too heavyweight for our use.
• async/await: regenerator-runtime is too heavyweight for our use, and async-to-promises is not yet complete enough to be safely used.
• async iterators: depends on both generators and async functions
• lifted template literal restrictions: we do not use tagged template literals, nor implement custom DSLs, otherwise we would enable this.

Install

npm install --save-dev babel-preset-daun

Usage

Add the preset to your .babelrc:

{
  "presets": ["daun"]
}

Targeting Environments

This module uses @babel/preset-env to target specific environments. Please refer to @babel/preset-env#targets for a list of available options.

For a list of browsers please see browserlist.

You may override the default list of targets by providing a targets key.

{
  "presets": [["daun", {
    "targets": {
      "chrome": 50,
      "ie": 11,
      "firefox": 45
    }
  }]]
}

Or inherit the default list of browsers and extend them using additionalTargets.

{
  "presets": [["daun", {
    "additionalTargets": {
      "chrome": 42,
      "ie": 8
    }
  }]]
}

Debugging

Enable debugging by providing a debug key.

{
  "presets": [["daun", {
    "debug": true
  }]]
}

Classes loose mode

By default, this preset will compile classes in normal mode. This is safer, but comes with a bundle size and runtime overhead. To compile classes in loose mode, set the looseClasses option to true:

{
  "presets": [["daun", {
    "looseClasses": true,
  }]]
}

The risks of enabling loose classes are outlined in the Babel docs.

Specifying a babel runtime version

By default @babel/plugin-transform-runtime will assume the oldest version of the runtime to avoid importing helpers that don't exist which would fail at runtime. This can result in newer helpers being inlined into modules (ex. objectSpread2) which increases bundle size.

To avoid this you can configure the preset to use the same version of the runtime that's installed in your package.json.

ex. If package.json has "@babel/runtime": "^7.5.5" then you can use:

{
  "presets": [["daun", {
    "runtimeVersion": "7.5.5",
  }]]
}

Note that this will result in a runtime breakage if the version passed into the preset is newer than the version of the babel runtime actually being used at build time.

Disabling plugin-transform-runtime

You can use the transformRuntime option to disable @babel/plugin-transform-runtime. Specifying false will disable the plugin. This option defaults to true.

Specifying module transforms

You can use the modules option to enable transformation of modules given to this preset:

{
  "presets": [["daun", {
    "modules": "auto"
  }]]
}

Both true and the option default auto will not transform modules if ES6 module syntax is already supported by the environment, or "commonjs" otherwise. false will not transform modules.

You can use the runtimeHelpersUseESModules option to prevent transformation of runtime helpers to CommonJS modules.

{
  "presets": [["daun", {
    "runtimeHelpersUseESModules": true
  }]]
}

true will not transform runtime helpers to CommonJS modules. false will transform runtime helpers to CommonJS modules. The option defaults to true if modules is set to false, and false otherwise.