columnHeaderHtml

Programmatically generates HTML that will be injected on the calendar's column headings.

This function will will receive a date object that represents a single column's date and must return an HTML string to be injected.

Example:

var calendar = new Calendar(calendarEl, {
  columnHeaderHtml: function(date) {
    if (date.getUTCDay() === 5) {
      return '<b>Friday!</b>';
    } else {
      return '<i>other day</i>';
    }
  }
});