JSFiddle - React, Tailwind, and code Playground

JavaScript

function formatDate(date) {
    var d = new Date(date),
        month = '' + (d.getUTCMonth() + 1),
        day = '' + d.getUTCDate(),
        year = d.getUTCFullYear();

    if (month.length < 2) month = '0' + month;
    if (day.length < 2) day = '0' + day;
	
    return [year, month, day].join('-');
}

function getDate_FQ(range){
	var now = new Date();
	switch(range){
		case 'Previous FQ':
			now.setMonth(now.getMonth()-3);
			break;
		case 'Next FQ':
			now.setMonth(now.getMonth()+3);
			break;
		case 'Current FQ':
			break;
	}
	var quarter = Math.floor((now.getUTCMonth() / 3));
	var firstDate = new Date(now.getUTCFullYear(), quarter * 3, 1);
	var endDate = new Date(firstDate.getUTCFullYear(), firstDate.getUTCMonth() + 3, 0);
	return([firstDate, endDate])
}

let [first, end] = getDate_FQ('Current FQ')
console.log(formatDate(first), formatDate(end))