Question

我这里有很多代码..基本上我想将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），如果它不是有效数字，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”）。我不明白我的代码在哪里出错，但是KEEPS会返回警报消息。

以下是代码：

 // 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);
    }

Answer 1

grade[grade.length]＆lt; ~~我这里的问题就是问题。

grade.push() - 在评分中添加新的输入消息。
grade[grade.length - 1] - 获取最后一个

-

//...

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]);

//...

Answer 2

这是你的问题

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

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

您的第一个声明正常。假设您的数组有一个元素，grade.length将返回1，这将是您下一个元素的索引。但在第二个语句中，grade.length将为2，而等级[2]未定义，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]);

Answer 3

grade.length在初始化后为0，然后在添加元素后变为1。它应该是：

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

Answer 4

如果您想查看var result = isNaN(convertedInput)结果

，请

使用parseInt

Javascript与数组的验证问题

4 个答案: