Look and say sequence in javascript.

look-and-say.js

function lookAndSay(number) {
  var regex = /(.)\1*/g;
  return number.toString().replace(regex, function(regexMatch) {
    return regexMatch.length.toString() + regexMatch.substring(0, 1);	
  });
}

// Usage
function init() {
  var number = 1;
  for (var i = 0; i < 6; i++) {
      number = lookAndSay(number);
      console.log(number);
  }
}

/* Output for init()

11
21
1211
111221
312211
13112221

*/