.babelrc

{
    "presets": ["flow"],
    "env": {
        // Duplications are inevitable due to strange .babelrc env merging:
        // babel/babel#5276. This can be simplified in Babel 7 using .babelrc.js.
        "production": {
            "presets": [["es2015", {"modules": false, "loose": true}]],
            "plugins": [
                "transform-class-properties",
                "transform-runtime",
                "version-inline",
            ],
        },
        "development": {
            "presets": [["es2015", {"modules": false, "loose": true}]],
            "plugins": [
                "transform-class-properties",
                "transform-runtime",
                "version-inline",
            ],
        },
        "test": {
            "presets": [["es2015", {"loose": true}]],
            "plugins": [
                "transform-class-properties",
                "transform-runtime",
                "version-inline",
            ],
        },
        "esm": {
            "plugins": [
                "transform-class-properties",
                "version-inline",
            ],
        },
    },
}