JSFiddle - React, Tailwind, and code Playground

HTML

<body>

	<table>
		<tbody>
		<tr>
			<td>
			<div>R$ 29,90</div>
		</td>
		<td>
		 	<input type="number">
		 </td>
		</tr>
		</tbody>
		<tr>
			<td> </td>
			<td>Total da compra</td>
			<td><div id="total">R$ 29,90</div></td>
			<td> </td>
		</tr>
		</table>

JavaScript

function moneyTextToFloat(text) { 
			var cleanText = text.replace("R$", " ").replace(",", ".");
			return parseFloat(cleanText);
		}

		function floatToMoneyText(value) {
			var text = (value < 1 ? "0" : " ") + Math.floor(value * 100);
			text = "R$ " + text;
			return text.substr(0, text.length - 2) + "," + text.substr(-2); 
		}
		
	var total = document.getElementById("total");
	var mostrar = moneyTextToFloat(total.innerHTML);
	alert(mostrar);
	var mostrarTexto = floatToMoneyText(total.innerHTML);
	alert(mostrarTexto);