{
  "presets": [
    ["@babel/preset-env",
      {
        "targets": {
          "browsers": ["> 1%", "last 2 versions"]
        }
      }
    ]
  ],
  "plugins": [
    ["@babel/plugin-proposal-class-properties"],
    ["@babel/plugin-transform-runtime", {
      "absoluteRuntime": false,
      "corejs": 2, // 下面详解 默认2
      "helpers": true, // 助手函数是否提取，同babel-plugin-transform
      "regenerator": true, // 同babel-plugin-transform
      "useESModules": false
    }]
  ]

}