Here is an example that uses these two functions. It implements a simple text encoding, designed to hide content of a message from casual users. It replaces each alphabetical character in the input text by its "complementary" character: A by Z, B by Y, etc:

function complement(s) {
  var sResult = "";
  var i = 0;
  var d = 0;
  
  for (i = 0; i < s.length; i++) {
    d = s.charCodeAt(i);
	if ((d >= 65) && (d <= 90)) {
	  d = 90 - (d -65);
    }
	sResult += String.fromCharCode(d);
  }

  return sResult;
}

And here is how you call this function to encode it twice:

var s = "A SECRET MESSAGE! ";
window.alert(s);
var sEncoded = complement(s);
window.alert(sEncoded);
s = complement(sEncoded);
window.alert(s);

The second encoding should give you the original message.

Learn more about the ASCII standard and its new replacement, the Unicode, in our Column 25, Unicode.

People who read this tip also read these tips:

• The Conditional Operator
• Finding a File's Parent Folder
• Counting Pages in A Print Job
• Advance Loading of External Scripts
• Inheriting and Overriding Methods