Babel plugin to ensure function declarations at the block level are block scoped.
$ npm install babel-plugin-transform-es2015-block-scoped-functions
.babelrc
{
"plugins": ["transform-es2015-block-scoped-functions"]
}
$ babel --plugins transform-es2015-block-scoped-functions script.js
require("babel-core").transform("code", {
plugins: ["transform-es2015-block-scoped-functions"]
});