NTR is meant for client side applications. It is not currently on npm.
Use the module as such:
var elementsToAutoResize = [
{ e: '#element1', s: 24 },
{ e: '#element2', s: 18 }
];
ntr(elementsToAutoResize);
Your elements will now automatically resize their text based on window size. The algorithm is simple, if the width of the window is larger than the height:
<scale factor, s> * <magic number .005> * <window height>^2 / <window width>
or, if the width is less than or equal to the height:
<scale factor, s> * <magic number .005> * <window width>