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.

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