BabelJS is a JavaScript transpiler which transpiles new features into old standard. With this, the features can be run on both old and new browsers, hassle-free. Babeljs comes with a wide range of features in the form of plugins, presets, polyfills, etc.

In short, Babeljs is a toolset which has all the required tools available with it and which helps the developers to use all the current features available in ECMA Script and yet not worry how it will be supported on browsers.