<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html><head>
<script>
window.onload = function() {
document.MMM = document.getElementsByName('MMM')[0];
document.MMM2 = document.getElementsByName('MMM')[1]
}
Number.prototype.sys = String.prototype.sys = function(s) {
var x = Number(this);
if (!x) return 'Ошибка'
x = x.toString(s);
return x;
}
</script>
</head><body>
<input type="text" name="MMM"><br>
<input type="button" value="hex" onclick="document.MMM2.value = document.MMM.value.sys(16)"><input type="button" value="oct" onclick="document.MMM2.value = document.MMM.value.sys(8)"><input type="button" value="bin" onclick="document.MMM2.value = document.MMM.value.sys(2)">
<input type="text" name="MMM">
</body></html>