JSFiddle - React, Tailwind, and code Playground

HTML

<table>
    <tr>
        <td id="tabela">
            <input type="text" id="tabelainput" class="janmembros" maxlength="3" name="janmembros" value="1" disabled>
        </td>
        <td id="tabela">
            <input type="text" id="tabelainput" class="janvisitantes" maxlength="3" name="janvisitantes" value="3" disabled>
        </td>
        <td id="tabela3" class="jantotal"></td>
    </tr>
</table>
<table>
    <tr>
        <td id="tabela">
            <input type="text" id="tabelainput" class="janmembros" maxlength="3" name="janmembros" value="1" disabled>
        </td>
        <td id="tabela">
            <input type="text" id="tabelainput" class="janvisitantes" maxlength="3" name="janvisitantes" value="2" disabled>
        </td>
        <td id="tabela3" class="jantotal"></td>
    </tr>
</table>
<table>
    <tr>
        <td id="tabela">
            <input type="text" id="tabelainput" class="janmembros" maxlength="3" name="janmembros" value="1" disabled>
        </td>
        <td id="tabela">
            <input type="text" id="tabelainput" class="janvisitantes" maxlength="3" name="janvisitantes" value="5" disabled>
        </td>
        <td id="tabela3" class="jantotal"></td>
    </tr>
</table>
<table>
    <tr>
        <td id="tabela"></td>
        <td id="tabela"></td>
        <td id="tabela3" class="total"></td>
    </tr>
</table>

JavaScript

var somatorio = 0;
$('table').each(function () {
    var $this = $(this),
        janmembros = parseInt($this.find(".janmembros").val(), 10),
        janvisitantes = parseInt($this.find(".janvisitantes").val(), 10);
    $this.find(".jantotal").html(janmembros + janvisitantes);
    somatorio += janmembros || 0;
});
$(".total").html(somatorio);