ApexCharts: Heatmap tooltip formatter

Question

I'm using apexcharts to display a heatmap chart:

The series are named with Date objects, which are formatted on the y-axis like this:

yaxis: {
    labels: {
        formatter: function(value){
            if(value instanceof Date){
                return value.toLocaleDateString(undefined, {year: 'numeric', month: 'long'});
            } else {
                return value;
            }
        }
    }
},

How can I get the same kind of formatting for the tooltips? They show the regular string representation of the date object instead, but I only want to show month and year (as on the y-axis):

Answer 1

Pass a tooltip value to the options array, and set a formatter for the title value of the y-axis in it:

tooltip: {
    y: {
        title: {
            formatter: function(value){
                if(value instanceof Date){
                    return value.toLocaleDateString(undefined, {year: 'numeric', month: 'long'});
                } else {
                    try {
                        return new Date(value).toLocaleDateString(undefined, {year: 'numeric', month: 'long'});
                    } catch (e) {
                        return value;
                    }
                }
            }
        }
    }
}

Make sure to check the type of the value passed to the formatter, and create a new Date-object, if neccessary.