function normalizeToArray(value) {
    return value instanceof Array
        ? value
        : value == null
        ? []
        : [value];
}
data could be [12, 2323, {value: 223}, [1221, 23], {value: [2, 23]}]
This helper method determine if dataItem has extra option besides value
@param {string|number|Date|Array|Object} dataItem