Example of Run-length encoding (RLE) compression in javascript

RLE.js

var blocks = ["A","A","A","A","A","A","A","A","A","A","A","A","B","B","A","C","C","C","C","D","D","D","D","A","A","E","E","E","A"];

function Encode(input){
  
  var segmentLength = blocks.length;
  var run = 0, current = '', last = '', encoded = '';

  current = last = blocks[0];
  for(var i = 1; i <= segmentLength; i++){  
    if(current !== last){  
      encoded += run + last;
    
      run = 0;
      last = current;
    }

    current = blocks[i];
    run++;
  }
  encoded += run + last;
  
  return encoded;
}

function Decode(input){
  var decoded = [];  
  var result = input.replace(/(\d+\D{1})/g, function (match) {
      var current = match.slice(-1)
      var run = match.slice(0, -1);
      decoded = decoded.concat(Array.apply(null, Array(parseInt(run))).map(String.prototype.valueOf,current));
    });
  
  return decoded;
}

var encoded = Encode(blocks);
var decoded = Decode(encoded);
var reEncode = Encode(decoded);
console.log("Raw: ", blocks)
console.log("Encoded: ", encoded);
console.log("Decoded: ", decoded);
console.log("Reencoded:",reEncode)

The problem is if you pass in something like XYZto Encode, you get 1X1Y1Z, which is actually longer.