{
  var some_func = function(arg1, arg2) {
    //some code here
  }
}

var variable = some_func(a1);

function foo(bar) {
    console.log(bar);
    console.log(baz);
}

> foo()
< undefined
< ReferenceError: Can't find variable: baz

i. Let n be the current value of n plus 1.

ii. If n is greater than argCount, let v be undefined
    otherwise let v be the value of the n’th element of args.

var some_func = function(arg1, arg2) {
     alert(arg1); alert(arg2);
  }

 some_func('a'); // alerts a and undefined
 some_func('a','b'); // alerts a and b

var x; // defined but has undefined value will not throw error Result in undefined
y; // not defined and throws a value. Result in ReferenceError