If you've already used JSON lang in your views, here's a handy package to extract all lang keys to language files. The package exports all your __(‘some text’) calls to language files.
https://github.com/kkomelin/laravel-translatable-string-exporter
Here's a video demo.
<iframe allowfullscreen="" frameborder="0" height="360" src="https://www.youtube.com/embed/AA2m-FzkuCw" width="640"></iframe>