<script language="javascript">
var i = 1;
sum = 0;
while (i<=20){
sum += i;
i++;
}
document.write("1+2+3+...+20="+sum)
</script>
<script language="javascript">
var i = 1;
sum = 0;
while (i<=20){
sum += i;
i++;
}
document.write("1+2+3+...+20="+sum)
</script>
转载于:https://www.cnblogs.com/cn-wsy/archive/2012/02/27/2370107.html