Fade the background color

This JavaScript fades the background color from one color to another.

This code should be placed immediately after the BODY tag:

<SCRIPT LANGUAGE="JavaScript">
<!-- JavaScript begins...

function makearray(n)
{
 this.length = n;
 for(var i = 1; i <= n; i++)
 this[i] = 0;
 return this;
}

hexa = new makearray(16);
for(var i = 0; i < 10; i++) hexa[i] = i;
hexa[10]="a"; hexa[11]="b"; hexa[12]="c";
hexa[13]="d"; hexa[14]="e"; hexa[15]="f";

function hex(i)
{
 if (i < 0) return "00";
 else if (i >255) return "ff";
 else return "" + hexa[Math.floor(i/16)] + hexa[i%16];
}

function setbgColor(r, g, b)
{
 var hr = hex(r); var hg = hex(g); var hb = hex(b);
 document.bgColor = "#"+hr+hg+hb;
}

function fade(sr, sg, sb, er, eg, eb, step)
{
 for(var i = 0; i <= step; i++)
 {
  setbgColor(Math.floor(sr * ((step-i)/step) + er * (i/step)),
  Math.floor(sg * ((step-i)/step) + eg * (i/step)),
  Math.floor(sb * ((step-i)/step) + eb * (i/step)));
 }
}

/* Usage:
 *   fade(inr,ing,inb, outr,outg,outb, step);
 * example.
 *   fade(0,0,0, 255,255,255, 255);
 * fade from black to white with very slow speed.
 *   fade(255,0,0, 0,0,255, 50);
 *   fade(0xff,0x00,0x00, 0x00,0x00,0xff, 50); // same as above
 * step 2 is very fast and step 255 is very slow.
*/

function fadein()
{
  fade(255,255,255, 0,0,0, 100);
}

function fadeout()
{
  fade(0,0,0, 255,255,255, 100);
}

/* do fadein */
fadein();

// JavaScript ends -->
</SCRIPT>