a = a + 5;

can be written as:

a += 5;

All math operators can be accelerated. The statement:

b = b - 8;

can be written as:

b -= 8;

and:

c = c % 2;

can be written as:

c %= 2;

We can rewrite the persistent random banner's code with accelerated math operators:

function refreshDocJSTOD(frequency) {
  var max = tips.length;
  var dateObj = new Date();
  switch(frequency) {
    case "month": // 0 - 11
      tipIndex = dateObj.getMonth();
      break
    case "dayOfTheMonth": // 1 - 31
      tipIndex = dateObj.getDate() - 1 // 0 - 30
      break;
    case "dayOfTheWeek": // 0 - 6
      tipIndex = dateObj.getDay();
      break;
    case "hour": // 0 - 23
      tipIndex = dateObj.getHours();
      break;
    case "now": // Default
    default:
      tipIndex = getRandomIndex(max);
   }
 tipIndex %= max;
 document.write(tips[tipIndex]);
}

function getRandomIndex(max) {
 var randomNum = Math.random();
 randomNum *= max;
 randomNum = parseInt(randomNum);
 if(isNaN(randomNum)) randomNum = 0; // for Netscape
 return randomNum;
}

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• Number Formatting in Netscape 6
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• The Bitwise XOR Operator
• Binary and Hexadecimal Notations
• Converting Zero-Leading Strings to Integers