数字加上一个数字是Javascript中的NaN

Question

我很生气这是多么愚蠢.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

你需要写timeCompletedInSeconds而不是timeCompletedInSecond第6行.你错过s了最后,这就是你得到的原因undefined + 3 = NaN.