const presets = [
  [
    '@babel/preset-env',
    {
      useBuiltIns: 'usage',
      corejs: {
        version: 3
      },
      targets: {
        edge: '17',
        firefox: '60',
        chrome: '67',
        safari: '11.1',
        ie: '9'
      }
    }
  ]
]
module.exports = {
  presets,
  // 开启babel缓存 plugin-transform-runtime
  // 第二次构建时，会读取之前的缓存，如果代码没有变化，就不重新构建
  plugins: [
    '@babel/plugin-transform-runtime',
    '@babel/plugin-proposal-class-properties',
    '@babel/plugin-syntax-dynamic-import'
  ]
}