I got a problem from format datetime of bootstrap datepicker. I want to covert datetime to format: 2021(R3)/11 This is my config:

$('.datepicker').datepicker({
format: {
    toDisplay: function (date, format, language) {
        var d = new Date(date);
        const year = d.getFullYear()
        const month = ('0' + (date.getMonth() + 1)).slice(-2);
        const era = getEra(date)
        return `${year}(${era})/${month}`;
    }, 
    toValue: function (date, format, language) {
        return new Date(date);
    }
}})

But there something make ${era} variable disappear in result:

[Result when change data][1] [1]: https://i.stack.imgur.com/mmhIb.png

It's look like round brackets been detected by something and remove every thing inside.

Have you guy have any idea ?

P/S: getEra(...) just return string