console
while 循环
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title></title>
<script>
var n = 1;
var sum = 0;
while(n<=100)
{
sum += n;
n++;
}
document.write(sum);
</script>
</head>
<body>
</body>
</html>
<br>
do…while循环：
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title></title>
<script>
var n = 1;
var sum = 0;
do
{
sum += n;
n++;
} while (n <= 100);
document.write(sum);
</script>
</head>
<body>
</body>
</html>
<br>
for循环：
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title></title>
<script>
var n = 1;
var sum = 0;
for (; n <= 100; n++)
{
sum += n;
}
document.write(sum);
</script>
</head>
<body>
</body>
</html>