自动检查并替换文本框内的字符

<HTML>
<HEAD>
<META http-equiv='Content-Type' content='text/html; charset=gb2312'>
<TITLE>自动检查并替换文本框内的字符</TITLE>

<SCRIPT LANGUAGE="JavaScript">
<!-- Begin
function replaceChars(entry) {
out = "a"; // 要替代的字母
add = "z"; // 替换后的字母
temp = "" + entry;

while (temp.indexOf(out)>-1) {
pos= temp.indexOf(out);
temp = "" + (temp.substring(0, pos) + add +
temp.substring((pos + out.length), temp.length));
}
document.subform.text.value = temp;
}
// End -->
</script>
</HEAD>
<BODY >