<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title></title>
</head>
<body>
<script>
// 计算1+2+3 ... +98+99+100的值
//1 .for循环
// 前测试循环
function sum_all() {
var result = 0;
for (var i = 0; i <= 100; i++) {
result += i;
}
return result
}
var s = sum_all();
alert(s);
//2. while()循环
// 前测试循环
function sum_all2() {
var result2 = 0;
var i = 0;
while (i <= 100) {
i++;
result2 += i;
}
return result2
}
alert(sum_all2());
// do-while语句
// 后测试循环语句
function sum_all3() {
var result3 = 0;
var i = 0;
do {
i++;
result3 += i;
}
while (i <= 100);
return result3
}
alert(sum_all3())
</script>
</body>
</html>
js-循环-计算1+2+3 ... +98+99+100的值
原文：http://www.cnblogs.com/webcode/p/6603788.html