square maxElements.js

function square(a) {
  return a*a;
}

function squareMaxElements (a,b,c) {
  var min = Math.min(a,b,c)
    , arr = [a,b,c]
    ;
  
  return arr = arr.filter(function (element) {
    return element !== min
  }).reduce(function(previous, next) {
    return square(previous) + square(next)
  });
}

Be liberal in what you accept, and conservative in what you send
or
Expect the worst. Behave your best.

Coul you provide more bullet proof solution?