JSFiddle - React, Tailwind, and code Playground

JavaScript

function formatNumber(val){
	
	val = Math.round(parseFloat(val));
	while (/(\d+)(\d{3})/.test(val.toString())){
		val = val.toString().replace(/(\d+)(\d{3})/, '$1'+','+'$2');
	}

	return '$ ' + val;

}

alert(formatNumber(1234567.89));