javascript

JavaScript to achieve the rainbow text effect method

The example of this article describes how JavaScript achieves the rainbow text effect. Share with you for your reference. The details are as follows:

<HTML>
<HEAD>
<TITLE>Rainbow Text</TITLE>
<SCRIPT LANGUAGE="JavaScript">
<!-- Begin hide from old browsers
function createHexArray(n)
{
 this.length = n;
 for (var i = 1; i <= n; i++)
 this[i] = i - 1;
 this[11] = "A";
 this[12] = "B";
 this[13] = "C";
 this[14] = "D";
 this[15] = "E";
 this[16] = "F";
 return this;
}
hx = new createHexArray(16);
function convertToHex(x)
{
 if (x < 17)
  x = 16;
 var high = x / 16;
 var s = high+"";
 s = s.substring(0, 2);
 high = parseInt(s, 10);
 var left = hx[high + 1];
 var low = x - high * 16;
 if (low < 1)
  low = 1;
 s = low + "";
 s = s.substring(0, 2);
 low = parseInt(s, 10);
 var right = hx[low + 1];
 var string = left + "" + right;
 return string;
}
function makeRainbow(text)
{
 text = text.substring(0, text.length);
 color_d1 = 255;
 mul = color_d1 / text.length;
 for(var i = 0; i < text.length; i++) {
  color_d1 = 255*Math.sin(i / (text.length / 3));
  color_h1 = convertToHex(color_d1);
  color_d2 = mul * i;
  color_h2 = convertToHex(color_d2);
  k = text.length;
  j = k - i;
  if (j < 0)
   j = 0;
  color_d3 = mul * j;
  color_h3 = convertToHex(color_d3);
  document.write("<FONT COLOR=\"#" + color_h3 + color_h1 +
  color_h2 + "\">" + text.substring(i, i + 1) + "</FONT>");
 }
}
// End hide from old browsers -->
</script>
</HEAD>
<body bgcolor="#FFFFCC">
<center>
<strong>
<font size=6>
<script>
<!--
// change to your own text ...
makeRainbow("Welcome to Boulder City Nevada");
document.write("<br>");
makeRainbow("The best dam city in the USA");
// -->
</script>
</font>
</strong>
</center>
</body>
</html>

I hope this article has been helpful to your javascript programming.