js成绩和闰年判断小案例3.25作业

1、建立测试数组；

2、用for循环挨个测试；

3、进行条件判断，并输出判断结果到HTML

4、在for循环内输出分隔线

<script type="text/javascript">
        var xs=[2001,2002,2003,2004,2005,2008,2020,3000,4000];
        for (var i = 8; i >= 0; i--) {
            x = xs[i];
            if(x%4 != 0){
                document.write(x+'不是闰年');
            }else if(x%400 == 0){
                document.write(x+'是闰年');
            }else if(x%100 == 0){
                document.write(x+'不是闰年');
            }else{
                document.write(x+'是闰年');
            }
            document.write('<hr>');

        }
        var grades=[10,20,30,40,50,60,70,80,90,100];
        for (var i = 9; i >= 0; i--) {
            grade = grades[i];
            if(grade<60){
                document.write('你考试-'+grade+'-分，不及格！！！');
            }else if(grade<70){
                document.write('你考试-'+grade+'-分，继续加油！');
            }else if(grade<90){
                document.write('你考试-'+grade+'-分，成绩良好');
            }else if(grade<100){
                document.write('你考试-'+grade+'-分，成绩优秀，注意休息');
            }else{
                document.write('你考试-'+grade+'-分，满分，没作弊吧？');
            }
            document.write('<hr>');
        }
    </script>

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执行效果

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以下是小结：

1、用+号连接变量名和字符串后，就可以在document.write()或alert()中输出变量值接字符串；

2、sublime的js的for循环默认写法，是从尾到头遍历的。