目录
2：打印出1-100之间的奇数和偶数,并求奇数“和”，和偶数“和”
4：弹出输入框接收班级人数，根据人数接收分数，计算班级平均数与总分数。
1.求1 - 100 之间的平均值和总和
var he = 0;
for (var i = 1; i <= 100; i++) {
he += i;
}
console.log('平均值是' + he / 100 + ',所有数总和是' + he)
2：打印出1-100之间的奇数和偶数,并求奇数“和”，和偶数“和”
var oddstr = ""; //储存奇数
var oddsum = 0; //存储奇数的和
var oddcount = 0; //奇数的个数
var evenstr = ""; //储存偶数
var evensum = 0; //存储偶数的和
var evencount = 0; //偶数的个数
for (var i = 1; i <= 100; i++) {
if (i % 2 == 0);
evenstr = evenstr + i + ",";
evensum = evensum + i;
evencount++;
} else {
oddstr = oddstr + i + ",";
oddsum = oddsum + i;
oddcount++;
}
console.log('奇数是：' + oddstr + "和" + oddsum + ",个数：" + oddcount);
console.log('偶数是：' + evenstr + "和" + evensum + ",个数：" + evencount);3：打印出1-100能被4整除的数，统计下个数
var division = 0; //整除的个数
var num = "";
for (var i = 1; i <= 100; i++) {
if (i % 4 == 0) {
num = num + i + ","
division++
}
}
console.log("1~100能被4整除的数有：" + num + "个数为：" + division); 4：弹出输入框接收班级人数，根据人数接收分数，计算班级平均数与总分数。
var people = prompt('输入班级人数')
var num = 0;
var gpa = 0;
// people = Number(people)
for (var i = 1; i <= people; i++) {
var sex = prompt('请输入第' + i + '位学生的成绩');
sex = Number(sex)
num = num + sex;
}
gpa = num / people;
console.log('总分为' + num + '\n' + '平均分数为' + gpa) 5：九九乘法表。
var str = "";
for (var i = 1; i <= 9; i++) {
for (var j = 1; j <= i; j++) {
str = str + j + "*" + i + "=" + j * i + "\t";
}
str = str + "\n";
}
console.log(str); 6：控制台接收两个数，打印出几行几列的；
var star = '';
var row = prompt('请输入要打印的行数：');
var cul = prompt('请输入要打印的列数：');
for (var i = 1; i <= row; i++) {
for (var j = 1; j <= cul; j++) {
star = star + '☆';
}
star = star + '\n'
}
console.log(star); 7：打印倒三角形案例
var str = '';
for (var i = 1; i <= 10; i++) { // 外层循环控制行数
for (var j = i; j <= 10; j++) { // 里层循环打印的个数不一样 j = i
str = str + '☆';
}
str += '\n';
}
console.log(str);
8：1-100之间的质数
for (var i = 2; i <= 100; i++) {
for (var j = 2; j <= i; j++) {
if (i % j == 0) {
break;
}
}
if (j >= i) {
console.log(i + ' ');
}
}