Code
function istogramma()
{
/*
*
* Prende in input una serie di numeri, sia positivi che negativi
* e crea un istogramma.
*/
var n = window.prompt('Numero di valori da inserire:', '');
n = parseInt(n); // rende il valore se valido Int altrimenti NaN
if(isNaN(n) == true)
{
document.write('<p align=\"center\"><b>Non hai selezionato nessun valore...</b></p>');
document.write('<br>');
}
else
{
var num = new Array();
var max = 0;
for(var i=0; i<n; i++)
{
var tmp = window.prompt('Inserire Valore [' + (i+1) + '/' + n + ']', '');
tmp = parseFloat(tmp);
if(isNaN(tmp) == true)
{
n = i;
break;
}
num[i] = tmp;
if(max < Math.abs(num[i])) max = Math.abs(num[i]);
}
for(var i=0; i<n; i++) num[i] *= 100/max;
document.write('<p align=\"center\"><b>Istogramma for JavaScript</b></p>');
document.write('<br>');
document.write('<table align=\"center\" border=\"0\" bgcolor=\"red\">');
document.write('<tr><td>');
document.write('<table align=\"center\" border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"200\" bgcolor=\"black\">');
for(var j=0; j<n; j++)
{
document.write('<tr>');
for(var i=0; i<200; i++)
{
var aux = num[j];
if(num[j] == 0) document.write('<td width=\"1\" bgcolor=\"white\"> </td>');
if(num[j] > 0 && i < 100) document.write('<td width=\"1\" bgcolor=\"white\"> </td>');
else if(num[j] > 0 && i >= 100)
{
if((i-100) <= aux)
document.write('<td width=\"1\" bgcolor=\"green\"> </td>');
else
document.write('<td width=\"1\" bgcolor=\"white\"> </td>');
}
if(num[j] < 0 && i < (100+aux)) document.write('<td width=\"1\" bgcolor=\"white\"> </td>');
else if(num[j] < 0 && (i >= (100+aux) && i < 100)) document.write('<td width=\"1\" bgcolor=\"yellow\"> </td>');
else if(num[j] < 0 && i >= 100) document.write('<td width=\"1\" bgcolor=\"white\"> </td>');
}
document.write('</tr>');
}
document.write('</table>');
document.write('</td></tr>');
document.write('</table>');
}
}
<html>
<head>
<title>Disegnare un Istogramma...</title>
<script src='istogramma.js' type='text/javascript'></script>
</head>
<body OnLoad="istogramma();">
</body>
</html>