-1

我这里有很多代码......基本上我想将我的全局变量转换为数组...... IE。等级数组。当我提示等级（提示）时，它应该验证输入是一个数字（通过 if 语句），如果它不是一个有效的数字，例如。一个字母，程序返回一个警报（“不是有效的输入，请输入有效的输入”）。我不明白我的代码哪里出错了，但它不断返回警报消息。

这是代码：

 // Loop through assignments
    for(var k = 1; k <= numberOfAssignments; k++) {

        // Print the first <td>
        document.write(table.dataopen);

        // Get the grade for the assignment
        var grades = new Object();
        grades.validrange = 0;
        grades.min = 0;
        grades.max = 100;

        var grade = new Array();
        do {
            grade[grade.length] = prompt("What's the grade for assignment " + k + "?");

            var convertedInput = parseInt(grade[grade.length]);

            // Using automatic conversion, if the original input and the converted input are the same,
            // we know we have a valid integer.
            var result = convertedInput == grade[grade.length];

            // If not a valid integer, let's show an appropriate error message. We use alert as
            // we may change how we report errors back.
            if(!result) {
                alert("Not a valid input. Please try again");
            }

            // Note the use of paranthesis; the first three clauses have to be all TRUE in order for the value in
            // the paranthesis to be true. In this context, we first check that all values are indeed numbers.
            // Then we check whether the grade is less than the min or greather than the max
            if((!isNaN(grade[grade.length]) && !isNaN(grades.min) && !isNaN(grades.max)) &&
                grade[grade.length] < grades.min || grade[grade.length] > grades.max) {

                // Invalid range, so show the error.
                alert("Valid ranges are between " + grades.min + " and " + grades.max);

                grades.validrange = false;
            }
            else {
                // If we came here, it means we didn't use the previous return, which in turns mean that the three
                // arguments are numbers AND the range is valid

                grades.validrange = true;
            }

        } while(!result || !grades.validrange);

        var score = parseInt(grade[grade.length]);

        // Display the grade
        document.write(score);

        // Keep track of the grades/scores (add to total)
        totalScore += score;

        // Print the </td>
        document.write(table.dataclose);
    }
4

4 回答 4

2

grade[grade.length]<~~ 我的事情是这里的问题。

  • grade.push()- 将新的输入消息添加到成绩中。
  • grade[grade.length - 1]- 得到最后一个

-

//...

grade.push(prompt("What's the grade for assignment " + k + "?"));
var lastIndex = grade.length - 1;

// Using automatic conversion, if the original input and the converted input are the same,
// we know we have a valid integer.
var convertedInput = parseInt(grade[lastIndex]);

//...
于 2013-07-07T03:39:43.733 回答
0

这是你的问题

grade[grade.length] = prompt("What's the grade for assignment " + k + "?");

var convertedInput = parseInt(grade[grade.length-1]);

您的第一个陈述效果很好。假设您的数组有一个元素，grade.length将返回 1，这将是您的下一个元素的索引。但是在第二个语句grade.length中将是 2 并且等级 [2] 是未定义的，因为您的数组只有两个元素（等级 [0] 和等级 [1]）。所以你的第二个陈述应该是

var convertedInput = parseInt(grade[grade.length-1]);
于 2013-07-07T03:41:29.853 回答
0

grade.length 初始化后为 0，添加元素后变为 1。它应该是：

var convertedInput = parseInt(grade[grade.length - 1]);
于 2013-07-07T03:43:58.667 回答
0

var result = isNaN(convertedInput)如果要检查parseInt结果，请使用

于 2013-07-07T04:03:00.617 回答