haiku.js

Array.prototype.pickRand = function () {
  return this[Math.floor(Math.random()*this.length)];
};

// grammar from Daniel Howe
// http://rednoise.org/rita/examples/p5js/HaikuGrammar/#source2

let grammar = {
  "start": "<5L> <7L> <5L>",
  "<5L>": "<1> <4>|<1> <3> <1>|<1> <1> <3>|<1> <2> <2>|<1> <2> <1> <1>|<1> <1> <2> <1>|<1> <1> <1> <2>|<1> <1> <1> <1> <1>|<2> <3>|<2> <2> <1>|<2> <1> <2>|<2> <1> <1> <1>|<3> <2>|<3> <1> <1>|<4> <1>|<5>",
  "<7L>": "<1> <1> <5L>|<2> <5L>|<5L> <1> <1>|<5L> <2>",
  "<1>": "red|white|black|sky|dawns|breaks|falls|leaf|rain|pool|my|your|sun|clouds|blue|green|night|day|dawn|dusk|birds|fly|grass|tree|branch|through|hell|zen|smile|gray|wave|sea|through|sound|mind|smoke|cranes|fish",
  "<2>": "drifting|purple|mountains|skyline|city|faces|toward|empty|buddhist|temple|japan|under|ocean|thinking|zooming|rushing|over|rice field|rising|falling|sparkling|snowflake",
  "<3>": "sunrises|pheasant farms|people farms|samurai|juniper|fishing boats|far away|kimonos|evenings|peasant rain|sad snow fall",
  "<4>": "aluminum|yakitori|the east village|west of the sun| chrysanthemums|cherry blossoms",
  "<5>":"resolutional|non-elemental|rolling foothills rise|toward mountains higher|out over this country|in the springtime again"
};

// 

class Grammar {

  constructor() {
    this.grammar = null;
  }

  load(src) {
    if (src &&
        src instanceof Object) {
      return this.grammar = src;
    }
    // else get the grammar file
  }

  expand(entry) {
    let start = entry|| this.grammar["start"],
        pick = start.split('|').pickRand();

    if (!/<[A-Z0-9]+>/.test(pick)) {
      return pick;
    }

    return pick.split(' ').map(word => {
      if (/^<[A-Z0-9]+>$/.test(word)) {
        return this.expand(this.grammar[word]);
      }
      return pick;
    }).join(' ');
  }

}

let g = new Grammar();
g.load(grammar);

console.log(g.expand());