Simple Markov text generator

markov.js

class Markov {
  constructor(text) {
    text = text.replace(/\./g, " . ");
    text = text.replace(/\s\s+/g, " ");
    this.map = {};
    let w1 = "";
    let w2 = "";
    text.split(/\s/).forEach(w3 => {
      if (!this.map[w1 + " " + w2]) this.map[w1 + " " + w2] = [];
      this.map[w1 + " " + w2].push(w3);
      w1 = w2;
      w2 = w3;
      if (w3 == ".") {
        w1 = "";
        w2 = "";
      }
    });
  }

  nextWord(w1, w2) {
    let choices = this.map[w1 + " " + w2];
    if (!choices) {
      return "";
    }
    let index = Math.floor(Math.random() * choices.length);
    return choices[index];
  }

  get sentence() {
    for (let i = 0; i < 100; i++) {
      let w1 = "";
      let w2 = "";
      let words = [];
      while (true) {
        let w3 = this.nextWord(w1, w2);
        if (!w3 || w3 == ".") {
          break;
        }
        words.push(w3);
        w1 = w2;
        w2 = w3;
      }
      if (words.length > 4 && words.join(" ").length < 140)
        return words.join(" ") + ".";
    }
    return "ERROR: Could not generate sentence."
  }

  fill(querySelector) {
    let el = document.querySelector(querySelector);
    el.innerText = this.sentence;
  }
}