gs_nuxt/node_modules/@nuxt/babel-preset-app/README.md

@nuxt/babel-preset-app

Default babel preset for nuxt

Usage

This is the default preset used by Nuxt, which is mainly a wrapper around the @babel/preset-env preset. It also optionally uses the @vue/babel-preset-jsx preset as well as @babel/plugin-proposal-decorators, @babel/plugin-proposal-class-properties, @babel/plugin-transform-runtime. Furthermore the preset is adding polyfills.

Note: Since core-js@2 and core-js@3 are both supported from Babel 7.4.0, we recommend directly adding core-js and setting the version via the corejs option.

yarn add --dev core-js@3 @babel/runtime-corejs3

# or

yarn add --dev core-js@2 @babel/runtime-corejs2

Usually, no additional configuration is required. If needed though, there is an option to fine-tune the preset's behavior. Just add the following to nuxt.config.js:

babel: {
  presets(env, [ preset, options ]) {
    return [
      [ "@nuxt/babel-preset-app", options ]
    ]
  }
}

env is an object which contains envName (server, client, modern) and all nuxtEnv properties (isDev, isServer, isClient, isModern, isLegacy)

preset is the preset package name @nuxt/babel-preset-app

options is an object with parameters, for example:

const options = {
  useBuiltIns: "entry"
}

Below is a list of all available options parameters:

Options

• bugfixes - @babel/preset-env
• configPath - @babel/preset-env parameter
• forceAllTransforms - '@babel/preset-env' parameter
• debug, default false - '@babel/preset-env' parameter
• decoratorsBeforeExport
• decoratorsLegacy, default true
• exclude - '@babel/preset-env' parameter
• ignoreBrowserslistConfig, defaults to value of modern - '@babel/preset-env' parameter
• include - '@babel/preset-env' parameter
• jsx, default true, can be a an object passed as params to @vue/babel-preset-jsx`
• loose, default false - '@babel/preset-env' parameter and also sets loose=true for @babel/plugin-proposal-class-properties
• modules, default false - '@babel/preset-env' parameter
• polyfills, default core-js@2: ['es6.array.iterator','es6.promise','es6.object.assign','es7.promise.finally'], core-js@3: ['es.array.iterator','es.promise','es.object.assign','es.promise.finally'], more in the corresponding repository
• shippedProposals - '@babel/preset-env' parameter
• spec - '@babel/preset-env' parameter
• targets - '@babel/preset-env' parameter
• useBuiltIns, default "usage" - '@babel/preset-env' parameter
• corejs, default { version: 2 } - '@babel/preset-env' parameter

There are detailed docs for the parameters of '@babel/preset-env'.

Example 1. Change targets for server and client respectively

export default {
  build: {
    babel: {
      presets({ envName }) {
        const envTargets = {
          client: { browsers: ["last 2 versions"], ie: 11 },
          server: { node: "current" },
        }
        return [
          [
            "@nuxt/babel-preset-app",
            {
              targets: envTargets[envName]
            }
          ]
        ]
      }
    }
  }
}

Example 2. Use core-js@3

NOTE: Make sure that all dependencies have been upgraded to use core-js@3. If core-js@2 and core-js@3 are both dependent, babel may resolve incorrect core-js package which is hoisted by yarn/npm.

yarn add --dev core-js@3 @babel/runtime-corejs3

export default {
  build: {
    babel: {
      // envName: server, client, modern
      presets({ envName }) {
        return [
          [
            '@nuxt/babel-preset-app',
            {
              corejs: { version: 3 }
            }
          ]
        ]
      }
    }
  }
}