JS Simple encryption

simple_encrypt.js

var key = "SXGWLZPDOKFIVUHJYTQBNMACERxswgzldpkoifuvjhtybqmncare";
// matches ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ

function encodeStr(uncoded) {
  uncoded = uncoded.toUpperCase().replace(/^\s+|\s+$/g,"");
  var coded = "";
  var chr;
  for (var i = uncoded.length - 1; i >= 0; i--) {
    chr = uncoded.charCodeAt(i);
    coded += (chr >= 65 && chr <= 90) ? 
      key.charAt(chr - 65 + 26*Math.floor(Math.random()*2)) :
      String.fromCharCode(chr); 
    }
  return encodeURIComponent(coded);  
}

function decodeStr(coded) {
  coded = decodeURIComponent(coded);  
  var uncoded = "";
  var chr;
  for (var i = coded.length - 1; i >= 0; i--) {
    chr = coded.charAt(i);
    uncoded += (chr >= "a" && chr <= "z" || chr >= "A" && chr <= "Z") ?
      String.fromCharCode(65 + key.indexOf(chr) % 26) :
      chr; 
    }
  return uncoded;   
}