module.exports = {
  presets: [
    '@vue/cli-plugin-babel/preset',
  ],
  plugins: ['transform-remove-strict-mode',
    [
      '@babel/transform-runtime', {
        absoluteRuntime: false,
      }],
    '@babel/plugin-proposal-optional-chaining',  // 可选链 ?.
    '@babel/plugin-proposal-nullish-coalescing-operator', // 空值合并 ??
  ],
  env: {
    development: {
      // babel-plugin-dynamic-import-node plugin only does one thing by converting all import() to require().
      // This plugin can significantly increase the speed of hot updates, when you have a large number of pages.
      // https://panjiachen.github.io/vue-element-admin-site/guide/advanced/lazy-loading.html
      plugins: ['dynamic-import-node'],
    },
  },
};