The markdown needed to generate journal headers in Joplin using the JavaScript plugin

headers.md

// Customise these
var monthOffset = 0  // how much to offset the month of headers, 0 is current month
var header = "h"  // include a toc? "y"es "h"idden or no (any input), no header is default

//Don't edit below this point
var thisMonth = new Date().getMonth()
var thisYear = new Date().getFullYear()

function getWeekdayFromDate(date) {
  const dayOfWeek = new Date(date).getDay();    
  return isNaN(dayOfWeek) ? null : 
    ['Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday'][dayOfWeek];
}

function getDaysInMonth(month, year) {
	return new Date(year, month+1, 0).getDate();
}

var output = ""

if (header == "y") {
	output = output.concat("${toc}\n\n* * *\n* * *\n\n")
} else if (header == "h") {
	output = output.concat("<details><summary>TOC</summary>\n\n${toc}\n\n</details>\n\n* * *\n* * *\n\n")
}

daysInMonth = Array.from(Array(getDaysInMonth(thisMonth+monthOffset, thisYear)).keys())

for (var i in daysInMonth) {
	var day = parseInt(i)+1
	var date = new Date(thisYear, thisMonth+monthOffset, day)
	output = output.concat("# ", day.toString().padStart(2, "0"), " ", getWeekdayFromDate(date), "\n\n\n")
}

return output