JavaScript案例：求学生成绩和打印九九乘法表

<script>
    var num = prompt('请输入班级总人数：');
    var sum = 0;
    var average = 0;
    for (var i = 1; i <= num; i++) {
        var score = prompt('请输入第' + i + '个的学生成绩：');
        sum = sum + parseFloat(score);//需要用到转换
    }
    average = sum / num;
    alert('班级总的成绩是' + sum);
    alert('班级的平均成绩是' + average);
</script>

<script>
    var str = '';
    for (var i = 1; i <= 9; i++) { //外层循环控制行数
        for (var j = 1; j <= i; j++) { //里层循环控制每一行的个数
            str += j + '*' + i + '=' + i * j + '\t';
        }
        str += '\n';
    }
    console.log(str);
</script>