Using computer date and adding a day indicator

Question

I have been trying to display the following "on this 4^th day of January in the year 2022"

using javascript on an HTML page

const monthNames = ["January", "February", "March", "April", "May", "June",
  "July", "August", "September", "October", "November", "December"
];
const d = new Date();
var dayn = d.getDay()
var dayString;
if (dayn == 1) {
  dayString = "</b><sup>st</sup>"
} else if (dayn == 3) {
  dayString = "</b><sup>rd</sup>"
} else if (dayn >= 4) {
  dayString = "</b><sup>th</sup>"
} else {
  dayString = "</b><sup>nd</sup>"
}
var dateStr = "<b>" + dayn + dayString + "</b> day of<b> " + monthNames[d.getMonth()] + "</b> in the year <b>" + d.getFullYear(); + "</b>"
document.write(dateStr);

but for some reason it is displaying today as the 2nd and not the 4th and

where I want to display ie. 4^th March 2022 (today +89 days) it is failing to do so...

So the aim is to on the first line display:

"on this 4^th day of January in the year 2022"

and on the next line

"no later than 3^rd day of March 2022"

Answer 1

const monthNames = ["January", "February", "March", "April", "May", "June",
  "July", "August", "September", "October", "November", "December"
];
const d = new Date();
var dayn = d.getDate();
var dayString;
if (dayn == 1) {
  dayString = "</b><sup>st</sup>"
} else if (dayn == 3) {
  dayString = "</b><sup>rd</sup>"
} else if (dayn >= 4) {
  dayString = "</b><sup>th</sup>"
} else {
  dayString = "</b><sup>nd</sup>"
}
var dateStr = "<b>" + dayn + dayString + "</b> day of<b> " + monthNames[d.getMonth()] + "</b> in the year <b>" + d.getFullYear(); + "</b>"
document.write(dateStr);

Answer 2

You have to use d.getDate() instead of d.getDay()

const monthNames = ["January", "February", "March", "April", "May", "June",
  "July", "August", "September", "October", "November", "December"
];
const d = new Date();
var dayn = d.getDate();
var endDate = d.setDate(dayn + 89);
var daym = new Date(endDate).getDate();

var dayString;
if (dayn == 1) {
  dayString = "</b><sup>st</sup>"
} else if (dayn == 3) {
  dayString = "</b><sup>rd</sup>"
} else if (dayn >= 4) {
  dayString = "</b><sup>th</sup>"
} else {
  dayString = "</b><sup>nd</sup>"
}

var endDayString;
if (daym == 1) {
  endDayString = "</b><sup>st</sup>"
} else if (daym == 3) {
  endDayString = "</b><sup>rd</sup>"
} else if (daym >= 4) {
  endDayString = "</b><sup>th</sup>"
} else {
  endDayString = "</b><sup>nd</sup>"
}
 
var endDateStr = "<b>" + daym + endDayString + "</b> day of<b> " + monthNames[d.getMonth()] + "</b> in the year <b>" + d.getFullYear(); + "</b>"
document.write(endDateStr);