code: function formatNumber(formatter, value) {
    // Spec treats -0 and +0 as 0.
    var number = TO_NUMBER(value) + 0;
  
    return %InternalNumberFormat(%GetImplFromInitializedIntlObject(formatter),
                                 number);
  }
docs: Returns a String value representing the result of calling ToNumber(value)
  according to the effective locale and the formatting options of this
  NumberFormat.