Javascript function not working correctly

Question

Good afternoon, I have the function below javascript to carry out the account when leaving the discount field:

function calcular1() {
  String.prototype.formatMoney = function() {
    var v = this;

    if (v.indexOf('.') === -1) {
      v = v.replace(/([\d]+)/, "$1,00");
    }

    v = v.replace(/([\d]+)\.([\d]{1})$/, "$1,$20");
    v = v.replace(/([\d]+)\.([\d]{2})$/, "$1,$2");
    v = v.replace(/([\d]+)([\d]{3}),([\d]{2})$/, "$1.$2,$3");

    return v;
  };
  var v1 = document.getElementById("txtValoraPagar").value;
  var v2 = document.getElementById("txtDesconto").value;
  var txtTotalPagar = document.getElementById("txtTotalPagar");
  if ((v2.replace("R$", "").replace(",", ".").replace(/\s*/g, '')) > (v1.replace(",", ".").replace(/\s*/g, ''))) {
    alert('Valor do desconto não pode ser maior do que o valor a receber.');
    document.getElementById("txtDesconto").value = '';
    return false;
  }
  if ((v1 != "") && (v2 != "") && (v1.replace(",", ".").replace(/\s*/g, '') >= v2.replace("R$", "").replace(",", ".").replace(/\s*/g, ''))) {
    txtTotalPagar.value = (eval(v1.replace(",", ".") - eval(v2.replace("R$", "").replace(",", "."))));
    txtTotalPagar.value = 'R$ ' + String(txtTotalPagar.value).formatMoney();
  }

For example, if the value is 15.00 and the discount is 5.00 it enters as if the discount was greater than the value, and informs Alert. Now if the value is 15.00 and I put the discount of 1.00, it works, and shows the total amount to pay right, of 14.00. By what to understand, he is counting the first number of the 15, q is 1, and takes the 5. I do not know why this is happening.

Answer 1

You have to compare numbers instead of characters.

Just another thing, name your most intuitive variables. You can’t have a variable named v1, v2. What do they mean? It becomes clearer variables with name 'value' and 'discount' which are what they really represent.

function calcular2() {
   var txtValor = document.getElementById("txtValoraPagar").value;
   var txtDesconto = document.getElementById("txtDesconto").value;
   var txtTotalPagar = document.getElementById("txtTotalPagar");
   var valor =0;
   var desconto =0; 
   if(txtValor != null)
     valor = Number(txtValor.replace(/[R\$ ]/g, '').replace(',', '.'));
   if(txtDesconto != null)
     desconto = Number(txtDesconto.replace(/[R\$ ]/g, '').replace(',', '.'));
   if(desconto > valor){
     alert('Valor do desconto não pode ser maior do que o valor a receber.');
     return false;
   }else if (valor >= desconto){
   	 txtTotalPagar.value = 'R$ ' + (valor - desconto);
   } 
}

Valor: <input type="text" id="txtValoraPagar" value="R$ ">
<br>
Desconto: <input type="text" id="txtDesconto" value="R$ ">
<br>
Total: <input type="text" id="txtTotalPagar" readonly="true" placeholder="Valor final">
<br>
<button onclick="calcular2()">Calcular</button>