code: function (content, delta) {
                  var output = [],
                      chunk, i, ln;
  
                  if (delta.length === 0) {
                      return content;
                  }
  
                  for (i = 0,ln = delta.length; i < ln; i++) {
                      chunk = delta[i];
  
                      if (typeof chunk === 'number') {
                          output.push(content.substring(chunk, chunk + delta[++i]));
                      }
                      else {
                          output.push(chunk);
                      }
                  }
  
                  return output.join('');
              }
docs: Delta patches content