Function which returns the smallest / largest numbers in a nested array structure
I shoudn't be able to think to this elegant and concise solution by myself! Notably because till now I didn't pay great attention to some of the acute features of JS.

So it was for me the opportunity to examine them deeper. From this I notice a possible little improvement, by slightly reducing the code, like this:

function getExtrema(structure, funct) {

  var ret = structure.map(function(value) {
    if (Array.isArray(value)) {
      return funct(...value);
    }
  });

  return ret;
}


Here is the working modified example: http://codepen.io/anon/pen/obYMmQ?editors=101.