chunkBy.js

String.prototype.chunkBy = function(len) {
  var current = len;
  var previous = 0;
  var stack = [];

  while (this[current]) {
    if (this[current++].match(/s+/)) {
      stack.push(this.substring(previous, current));
      previous = current;
      current += len;
    }
  }

  stack.push(this.substr(previous));
  return stack;
};