What pattern should I use for making a listen bot in Node/JavaScript?

I'm currently using Node to make my first bot, but I'm a little bit confused as to how I can make this into reality. The question is, what is the best pattern and name of the pattern I should use for this kind of stuff?

Basically, a person can listen to a subject and the speaker.

var test = person("ask_name","hallo person you are special");
console.log(test); // should return thanks!

var test = person("ask_name","hallo person you are dumb as the bird");
console.log(test); // should return i hate you!

function person(ability, body) {

  console.log(ability,body);
  var ability_name = "ability_" + ability;
  console.log(ability_name,typeof ability_name); // ignore all of this, trying something
  if (typeof ability_name) {};

  // ability list array
  var ability = [];

  // Search for ability
  // not done

  var say_bad = function() {
    this.listen_subject = 'ask_name';
    this.listen_body = 'you are dumb';
    return "i hate you!"
  }

  var say_good = function() {
    this.listen_subject = 'ask_name';
    this.listen_body = 'you are special';

    return "thanks!"
  }
}

Sorry, for not completing the code but this is the furthest I can go.