求和数返回NaN

Question

我想在div里面做一些数字,所以,我做了:

$(document).ready(function() {
    var numbers, sumNumbers;

    $(".item").each(function() {
  	numbers = $(this).children().text();
        numbers = +numbers;
    
        sumNumbers += numbers;
    });
  
    console.log(sumNumbers);
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

<div class="item">
  <span class="itemNum">0</span>
</div>

<div class="item">
  <span class="itemNum">2</span>
</div>

<div class="item">
  <span class="itemNum">1</span>
</div>

但是,同样numbers将从文本转换为数字与+numbers返回NaN,为什么？我已经尝试Number(numbers)过,但结果是一样的.

Answer 1

你没有初始化sumNumbers,所以得到undefined+数字=NaN

var numbers, sumNumbers = 0;