MRANK function for Google Sheets

Code.gs

function MRANK(value,values) {
  var values = values.map(function(x) { return x[0]; }); // apparently I misjudged how Google Sheets passes values. Why is it like this?!?!
  var valuesSorted = values.sort(function(a,b){ return b-a; });
  var valuesUnique = valuesSorted.filter(function(value,index,self) { return self.indexOf(value) === index; });
  var index = valuesUnique.indexOf(value);
  if (index<0) {
    throw("MRANK has no valid input data");
  }
  return index+1;
}