pvdz.ee - 11.2.3 Function calls

CallExpression : MemberExpression Arguments
CallExpression : CallExpression Arguments

Both are evaluated the same:

Code: (Meta Ecma)

function evaluate(MemberExpression Arguments) {
  var ref = evaluate(MemberExpression);
  var func = GetValue(ref);
  var argList = evaluate(Arguments); // returns List
  if (Type(func) != 'object') throw TypeError;
  if (!IsCallable(func)) throw TypeError;
  var thisValue = undefined;
  if (Type(ref) == 'reference') {
    if (IsPropertyReference(ref)) thisValue = GetBase(ref);
    else thisValue = GetBase(ref).ImplicitThisValue(); // ref is environment record
  } // else ref is undefined, so thisValue is undefined as well
  return func.[[Call]](thisValue, argList);
}

Native functions will never return a Reference. Host objects (custom by the implementation) may return a Reference but if they do, they must always return a non-strict Reference.