Practicing JSON API

im following this video tutorial by coding train from the series working with data

i save the files according to the vdieo same extensions
like sketch.js and the .json file
but everytime i run the js file it displays the js file in browser
i knew this would happen
but what is he using in this video that this json file runs on his browser?
is he using some special browser or some special code editor?
i know he using linux os please help im on windows 7