Console rainbow

gistfile1.js

function colorText(str) {
  var phase = 0;
  var outputStr = new Array();
  var args = new Array();
  var center = 128;
  var width = 127;
  var frequency = Math.PI*2/str.length;
  var red, green, blue, i;

  function componentToHex(c) {
    var hex = Math.round(c).toString(16);
    return hex.length == 1 ? "0" + hex : hex;
  }

  function rgbToHex(r, g, b) {
      return "#" + componentToHex(r) + componentToHex(g) + componentToHex(b);
  }

  for (i = 0; i < str.length; i++) {
    red   = Math.sin(frequency*i+2+phase) * width + center;
    green = Math.sin(frequency*i+0+phase) * width + center;
    blue  = Math.sin(frequency*i+4+phase) * width + center;
    hex = rgbToHex(red, green, blue);
    args.push('color:'+ hex +'');
    outputStr.push('%c' + str.charAt(i))
  }

  args.unshift(outputStr.join(''));
  console.log.apply(console, args);
}

colorText('Oh console rainbow text, you made my day!');