数字加数字在Javascript中为NaN

Question

我为这有多愚蠢而发火。这怎么可能？

  console.log(typeof form.timeCompletedInSeconds);
  console.log(typeof totalTimeCompletion);

  console.log(totalTimeCompletion);
  console.log(form.timeCompletedInSeconds);

  totalTimeCompletion = form.timeCompletedInSecond + totalTimeCompletion;
  console.log(totalTimeCompletion)

输出：

number
number
0
3
NaN

Answer 1

您需要在第6行写timeCompletedInSeconds而不是timeCompletedInSecond。最后遗漏了s，这就是为什么得到undefined + 3 = NaN的原因。