javascript - if 和 else if 和 else - javascript

Question

我刚刚开始学习 Javascript，我正在努力解决 if 和 else if 的用法。这是我的代码。问题是无论输入什么数字，它最后都会显示“无”结果。你能给我解释一下吗？

<script type="text/javascript">
    var grades,scores;
    scores=prompt ('write your score to convert it to grades');
    if (scores>101)
    grades='high distinction';
    else if (scores>91)
    grades='distinction';
    else if (scores>81)
    grades='credit';
    else if (scores>71)
    grades='pass';
    else if (scores>61)
    grades='fail';
    else (scores<60)
    grades='none';
document.write ('your grade name is'+grades);

    </script>

Answer 1

提示的结果始终是一个字符串。为了安全起见，先将其转换为数字:

scores = Number(prompt('write your score to convert it to grades'));

此外，您的代码在这里:

else(scores < 60)
grades = 'none';

else 不接受这样的条件。要么使用 else-if:

else if (scores < 60) grades = 'none';

或者只是其他:

else grades = 'none';

全文:

var grades, scores;
scores = Number(prompt('write your score to convert it to grades'));
if (scores > 101)
  grades = 'high distinction';
else if (scores > 91)
  grades = 'distinction';
else if (scores > 81)
  grades = 'credit';
else if (scores > 71)
  grades = 'pass';
else if (scores > 61)
  grades = 'fail';
else grades = 'none';
document.write('your grade name is' + grades);