Question

我的函数应该返回一个数字，但它会一直返回＆＃34; undefined，＆＃34;我已经通过我的教科书，无法弄清楚我哪里出错了。我不确定我是否正确定义了我的变量，但是我被卡住了，任何方向都会受到赞赏。

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
          "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <meta charset="utf-8" />
        <title>Greendale Community College</title>
    <script type="text/javascript">
    /* <![CDATA[ */
    /* ]]> */
    var creditTotal = document.getElementsByName("numCredits");
    var tuitionCost = 0;
    function calcTuition() {
        tuitionCost = 302 * creditTotal;
    }

</script>
</head>
<body>
    <p><center><font face="impact" font size="200" color="green">Greendale Community College</font></center></p>
    <center><img src="greendale.jpg" alt="greendale" width="512" height="256"/></center>
    <h1><center>Tuition Calculator</center></h1>
    <form name="tuitionCalculator" action="" method="get">
    <h2>Semester</h2>
    <h3>(choose a semester)</h3>
        <input type="radio" name="semesterFall"/> Fall 2018 <br />
        <input type="radio" name="semesterSpring"/> Spring 2018 <br />
        <input type="radio" name="semesterSummer"/> Summer 2018 <br />
    <h2>Residency</h2>
    <h3>(choose your residency)</h3>
        <input type="radio" name="instate" /> In-State <br />
        <input type="radio" name="outstate" /> Out-of-State <br />
        <input type="radio" name="international" /> International <br />
    <h2>Credits</h2>
    <h3>(enter your number of credits)</h3>
        <input type="text" size="2" maxlength="2" name="numCredits" /><br />
            <input type="button" onclick="window.alert(calcTuition())" value="Calculate Your Tuition" />
            </form>
    </body>
</html>

Answer 1

document.getElementsByName("numCredits")是具有tagName numCredits的所有元素的集合。您需要使用[0]指定前一个。
document.getElementsByName("numCredits")[0].value是给你输入值的那个。然后不要忘记parseInt它为整数。

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
          "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <meta charset="utf-8" />
        <title>Greendale Community College</title>
    <script type="text/javascript">
    /* <![CDATA[ */
    /* ]]> */
    
    function calcTuition() {
      var tuitionCost = 0;
        var creditTotal = document.getElementsByName("numCredits")[0].value;
       console.log(creditTotal);
        tuitionCost = 302 * parseInt(creditTotal);
      return tuitionCost;
    }

</script>
</head>
<body>
    <p><center><font face="impact" font size="200" color="green">Greendale Community College</font></center></p>
    <center><img src="greendale.jpg" alt="greendale" width="512" height="256"/></center>
    <h1><center>Tuition Calculator</center></h1>
    <form name="tuitionCalculator" action="" method="get">
    <h2>Semester</h2>
    <h3>(choose a semester)</h3>
        <input type="radio" name="semesterFall"/> Fall 2018 <br />
        <input type="radio" name="semesterSpring"/> Spring 2018 <br />
        <input type="radio" name="semesterSummer"/> Summer 2018 <br />
    <h2>Residency</h2>
    <h3>(choose your residency)</h3>
        <input type="radio" name="instate" /> In-State <br />
        <input type="radio" name="outstate" /> Out-of-State <br />
        <input type="radio" name="international" /> International <br />
    <h2>Credits</h2>
    <h3>(enter your number of credits)</h3>
        <input type="text" size="2" maxlength="2" name="numCredits" /><br />
            <input type="button" onclick="window.alert(calcTuition())" value="Calculate Your Tuition" />
            </form>
    </body>
</html>

功能显示为未定义

1 个答案: