Use getDimensionFilters API

var values = Table_1.getDataSource().getDimensionFilters("COUNTRY"); // 'values' is an array of FilterValue objects

var value = Table_1.getDataSource().getDimensionFilters("COUNTRY")[0];
switch (value.type) {
    case FilterValueType.Single:
        var singleValue = cast(Type.SingleFilterValue, value);
        console.log(singleValue.value); // can access the 'value' property now
        break;
    case FilterValueType.Multiple:
        var multipleValue = cast(Type.MultipleFilterValue, value);
        console.log(multipleValue.values); // can access the 'values' property now
        break;
    case FilterValueType.Range:
        var rangeValue = cast(Type.RangeFilterValue, value);
        console.log(rangeValue.from); // can access the 'from' property now
        console.log(rangeValue.to);   // can access the 'to' property now
        // further range properties: 'less', 'lessOrEqual', 'greater', 'greaterOrEqual'
        break;
    default:
        break;
}