Example shown in http://recodes.co/create-blessed-custom-wigets/

create-blessed-custom-widgets.js

var Blessed = require('blessed');

var screen = Blessed.screen({
  smartCSR: true,
  useBCE: true
});

var ChatHistory = function (options) {
  if (!(this instanceof Blessed.Node)) {
    return new ChatHistory(options);
  }

  options = options || {};
  options.shrink = true;
  Blessed.Element.call(this, options);
};

ChatHistory.prototype = Object.create(Blessed.Element.prototype);
ChatHistory.prototype.type = 'chatHistory';

// Define a instance property called `messages` that will store the message list.
ChatHistory.prototype._messages = [];

/**
 * Add a message to the history.
 * @param {String} msg
 */
ChatHistory.prototype.addMessage = function (msg) {
  var self = this;

  // Store the message into the widget list.
  this._messages.push(msg);
};

ChatHistory.prototype.render = function () {
  // Set the widget content.
  this.setContent(this._messages.join('\n'));

  // Call the super.
  return this._render();
};

// Create a new `ChatHistory` instance.
var chat = ChatHistory({
  height: '100%',
  padding: 1,
  tags: true,
  width: '100%'
});

// Display dummy messages.
chat.addMessage('People assume that time is a strict progression of cause to effect,');
chat.addMessage('but {underline}actually{/underline} from a non-linear, non-subjective viewpoint -');
chat.addMessage('it\'s more like a big ball of wibbly wobbly... time-y wimey... stuff.');

// Append the chat to the screen.
screen.append(chat);

// Render the screen.
screen.render();