Markov text generator example ftw. Run with `node markov_greeter.js` several times to watch it do its magic.

markov_greeter.js

// TRANSITION DAG
//////////////////////////////////////////////////////////////////////////////

let areYou = {
  value: " are you!",
  transitions: []
};

let questionMark = {
  value: "?",
  transitions: []
};

let today = {
  value: " today",
  transitions: [
    {
      probability: 1,
      to: questionMark
    }
  ]
}

let doing = {
  value: " doing",
  transitions: [
    {
      probability: 0.5,
      to: questionMark
    },
    {
      probability: 0.5,
      to: today
    }
  ]
};

let there = {
  value: ", there",
  transitions: [
    {
      probability: 1,
      to: areYou
    }
  ]
};

let everyone = {
  value: " everyone!",
  transitions: []
};

let areYou_Doing = {
  value: " are you",
  transitions: [
    {
      probability: 0.5,
      to: doing
    },
    {
      probability: 0.5,
      to: questionMark
    }
  ]
};

let isEveryone = {
  value: " is everyone",
  transitions: [
    {
      probability: 0.5,
      to: doing
    },
    {
      probability: 0.5,
      to: questionMark
    }
  ]
};

let commaHow = {
  value: ", how",
  transitions: [
    {
      probability: 0.5,
      to: areYou_Doing
    },
    {
      probability: 0.5,
      to: isEveryone
    }
  ]
};


let entry = {
  value: "Hello",
  transitions: [
    {
      probability: 0.40,
      to: everyone
    },
    {
      probability: 0.40,
      to: commaHow
    },
    {
      probability: 0.20,
      to: there
    }
  ]
};


// CODE
//////////////////////////////////////////////////////////////////////////////


function transition(transitions){
  if(transitions.length == 0){
    return "";
  }
  let random = Math.random();
  for(let transition of transitions){
    if(transition.probability > random){
      return generate(transition.to);
    } else {
      random -= transition.probability;
    }
  }
}

function generate( entry ){
  return  entry.value + transition(entry.transitions);
}

console.log(generate(entry));
console.log(generate(entry));
console.log(generate(entry));
console.log(generate(entry));
console.log(generate(entry));
console.log(generate(entry));
console.log(generate(entry));
console.log(generate(entry));
console.log(generate(entry));
console.log(generate(entry));
console.log(generate(entry));
console.log(generate(entry));
console.log(generate(entry));
console.log(generate(entry));
console.log(generate(entry));
console.log(generate(entry));
console.log(generate(entry));
console.log(generate(entry));
console.log(generate(entry));
console.log(generate(entry));
console.log(generate(entry));
console.log(generate(entry));