帮忙看看并解释这段代码的算法，谢谢

[regbbs66]

        <!--
document.write(unescape("<script language="javascript">%0D%0A<!--%0D%0Afunction check(form){%0D%0A%09var pass = "'2s4r4P7,8k5a:::f2{5T2";%0D%0A%09var newPass)0= "";%0D%0A%09for(i=1;i<pass.length;i+=2){%0D%0A%09    if(pass.charCodeAt(i) == 32)%0D%0A%09        newPass =)0newPass + "~";%0D%0A%09    else%0D%0A%09    9newPass)0=)0newPass)0+)0String.fromCharCode(pass.charCodeAt(i) - 1);%0D%0A    }%0D%0A%09form.Password.value =)0newPass;%0D%0A%09form.submit();%0D%0A%09return false;%0D%0A}%0D%0A//-->%0D%0A</script>"));
        //-->

[wuyg719]

<script language="javascript">
<!--
function check(form){
var pass = "'2s4r4P7,8k5a:::f2{5T2";
var newPass)0= "";
for(i=1;i<pass.length;i+=2){
if(pass.charCodeAt(i) == 32)
newPass =)0newPass + "~";
else
9newPass)0=)0newPass)0+)0String.fromCharCode(pass.charCodeAt(i) - 1);
}
form.Password.value =)0newPass;
form.submit();
return false;
}
//-->
</script>