.babelrc

{
  "env": {
    "babel6": {
      "plugins": [
        ["transform-es2015-block-scoping", {
          "throwIfClosureRequired": true
        }],
        "transform-flow-strip-types"
      ]
    },
    "test": {
      "plugins": [
        ["@babel/plugin-transform-block-scoping", {
          "throwIfClosureRequired": true
        }],
        "@babel/plugin-transform-flow-strip-types",
        "@babel/plugin-transform-modules-commonjs"
      ]
    },
    "commonjs": {
      "plugins": [
        ["@babel/plugin-transform-block-scoping", {
          "throwIfClosureRequired": true
        }],
        "@babel/plugin-transform-flow-strip-types",
        "@babel/plugin-transform-modules-commonjs"
      ]
    },
    "es": {
      "plugins": [
        ["@babel/plugin-transform-block-scoping", {
          "throwIfClosureRequired": true
        }],
        "@babel/plugin-transform-flow-strip-types"
      ]
    }
  }
}