matrix-js-sdk/.babelrc

{
    "presets": ["es2015"],
    "plugins": [
        // this transforms async functions into generator functions, which
        // are then made to use the regenerator module by babel's
        // transform-regnerator plugin (which is enabled by es2015).
        "transform-async-to-bluebird",

        // This makes sure that the regenerator runtime is available to
        // the transpiled code.
        "transform-runtime",
    ],
}