> I'm not familiar with that behaviour. Do you mean automatically watching and compiling on changes?

I mean that a javascript library would act as a gate to live-compile Javascript files on-the-fly.

For example, with ES6-Module-Loader[1], you can do something like this in your browser :

    <script>
        System.import('mymodule').then(function(m) {
            new m.q();
        }).catch(console.error.bind(console));
    </script>

'mymodule' can be an uncompiled ES6 module, the code will still work fine, because ES6-Module-Loader will get its content (XHR), resolve its dependencies, then pass everything to Traceur.

Obviously its main use is for debug purpose (since it does a request for each source file, which won't be great until HTTP 2), but it allows to have a full ES6 workflow, without any visible compilation pass.

[1] https://github.com/ModuleLoader/es6-module-loader