Sum numbers returns NaN
<p>I'm trying to do a sum of numbers inside div's, so, I did:</p>

<p><div class="snippet" data-lang="js" data-hide="false">
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<pre class="snippet-code-js lang-js prettyprint-override"><code>$(document).ready(function() {
    var numbers, sumNumbers;

    $(".item").each(function() {
   numbers = $(this).children().text();
        numbers = +numbers;
    
        sumNumbers += numbers;
    });
  
    console.log(sumNumbers);
});</code></pre>
<pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"&gt;&lt;/script&gt;

&lt;div class="item"&gt;
  &lt;span class="itemNum"&gt;0&lt;/span&gt;
&lt;/div&gt;

&lt;div class="item"&gt;
  &lt;span class="itemNum"&gt;2&lt;/span&gt;
&lt;/div&gt;

&lt;div class="item"&gt;
  &lt;span class="itemNum"&gt;1&lt;/span&gt;
&lt;/div&gt;</code></pre>
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</p>

<p>But, same converting the <code>numbers</code> from text to number with <code>+numbers</code> is returned NaN, why? I've already tried with <code>Number(numbers)</code> too but the result is the same.</p>