Simple functions to compress/uncompress javascript unicode strings using repeating patterns

compress.js

// Compress/Uncompress javascript unicode strings using repeating patterns
// Copyright 2015 davidpennington.me

function compress(str) {

  var original = str;

  // We don't allow newlines
  str = str.replace(/(\r\n|\n|\r)/gm,"");

  // Quote all digits (we don't want to parse them)
  str = str.replace(/(\d)/g, "\\$1");

  // Prepare our regex matcher
  var regex = RegExp(/(.+)(?=.*\1)/g);

  var matches = str.match(regex).sort(function(a, b){
    return (str.split(b).length * b.length) - (str.split(a).length * a.length);
  });

  var dict = [];
  for (index = 0; index < matches.length; ++index) {
    var word = matches[index];
    var len = word.length;

    // Only store a dictonary of 10 words 0-9
    if(word.length === 1) { continue; }
    if(dict.length === 10) { break; }

    var parts = str.split(word);

    // This word must exist at least twice in the string
    if(parts.length < 3) { continue; }

    dict.push(word);
    str = parts.join(dict.length - 1);

  }

  str = dict.join("\n") + "\n" + str;

  if((str.length + (str.length / 10)) < original.length) {
    return str;
  }

  return original;
}


function uncompress(str) {
  var dict = str.split("\n");

  if(dict.length === 1) return str;

  var str = dict.pop();

  str = str.replace(/\d/g, function(v, i) {
    if (str[i - 1] !== '\\') {
      return dict[v];
    }
    return v;
  });

  str = str.replace(/\\(\d)/g, "$1");

  return str;
}


var words = [
  '_send_T_send_send_ack-new_amend_pending-cancel-replace_replaced_cancel_pending-cancel-replace_replaced',
  'the quick brown fox jumped over the lazy dog',
  'This property returns the number of code units in the string.',
  'Not the result of the voodoo that replace will do that is apparently substituting $1 for the first capture group.',
  'What would your life look like if you were totally forgiven, completely justified, and eternally secure? Not a trick question.'
];

for (i = 0; i < words.length; ++i) {
  var str = words[i];
  console.log(str.length, str);
  console.log('compress', compress(str).length);
  console.log('uncom', uncompress(compress(str)).length, uncompress(compress(str)));
}

http://codepen.io/Xeoncross/pen/azPaJP?editors=101