codice:
<html> 
<head> 
<title>...</title>
<script language="javascript" type="text/javascript">
var num_a='123105678910';
var num_b='10234567899';

var arr_a=new Array();
var arr_b=new Array();
var arr_axb=new Array();

function riempi_array(num,arr){
	for (var j=0, k=0; k<num.length; k++){
		if(num.charAt(k)=='0' && num.charAt(k-1)=='1') arr[j-1]='10'
		else {
			arr[j]=num.charAt(k); j++
		}
	}
}

riempi_array(num_a,arr_a);
riempi_array(num_b,arr_b);

// riempi array prodotti;
for (var k=0;k<arr_a.length;k++){
	arr_axb[k]=parseInt(arr_a[k]*arr_b[k])
}
</script>
</head>
<body>
<script language="javascript" type="text/javascript">
document.write('a='+num_a+'
b='+num_b+'

<table border="1"><tr><th>a</th><th>b</th><th>axb</th></tr>');
for (var k=0;k<arr_axb.length;k++){
	document.write('<tr><td>'+arr_a[k]+'</td><td>'+arr_b[k]+'</td><td>='+arr_axb[k]+'</td></tr>');
}
document.write('</table>');
</script>
</body> 
</html>
supponendo che pippo (num_b) sia sempre "lungo" (il 10 vale come un carattere) quanto pesi (num_a)