individual characters treated as string in javascript arguments

Question

I need to write a function that retrieves the last parameter passed into the function. If it's just arguments, it should return the last element. If it's a string, it should return the last character. Arrays should return the last element of the array. My code works for arrays, strings and arguments as long as they are not all strings.

function last(list){
  var arr;
  if(list instanceof Array){
    return list[list.length-1];
  }
  if(typeof list === 'string' || list instanceof String){
    arr = list.split("");
    return arr[arr.length-1];
  }

  return arguments[arguments.length-1];
}

This works for almost every case, but I have a problem when the input is a bunch of string arguments.

Test.assertEquals(last('a','b','c','z'), 'z');

returns 'a'

Why are disjoint strings evaluating to true when testing if the arguments are arrays or strings and how can I universaly access the last value of arbitrary parameters?

Answer 1

Something like this should do that

function last(){
    var a = arguments;
    return (a.length > 1 ? [].slice.call(a) :
            typeof a[0] === 'string' ? a[0].split('') : a[0]).pop();
}

FIDDLE