Usar para declaración de bucle
<!DOCTYPE html>
<html>
<head lang="en">
<meta charset="UTF-8">
<title>使用for循环语句求出1~100的和</title>
</head>
<body>
<script>
var a=0;
for(b=1;b<=100;b++){
a+=b;
}
document.write(a);
</script>
</body>
</html>
Usar sentencia while loop
<!DOCTYPE html>
<html>
<head lang="en">
<meta charset="UTF-8">
<title>使用while循环语句求出1~100的和</title>
</head>
<body>
<script>
var a=0;b=1;
while(b<=100){
a+=b;
b++;
}
document.write(a);
</script>
</body>
</html>