var tracery = require('tracery-grammar');
var grammar = tracery.createGrammar({
  'animal': ['panda','fox','capybara','iguana'],
  'emotion': ['sad','happy','angry','jealous'],
  'origin':['I am #emotion.a# #animal#.'],
});
grammar.addModifiers(tracery.baseEngModifiers); 
console.log(grammar.flatten('#origin#'));

// Stable random number generator
// Copied from this excellent answer on Stack Overflow: https://stackoverflow.com/a/47593316/3306
function splitmix32(seed) {
  return function() {
    seed |= 0; // bitwise OR ensures this is treated as an integer internally for performance.
    seed = seed + 0x9e3779b9 | 0; // again, bitwise OR for performance 
    let t = seed ^ seed >>> 16;
    t = Math.imul(t, 0x21f0aaad);
    t = t ^ t >>> 15;
    t = Math.imul(t, 0x735a2d97);
    return ((t = t ^ t >>> 15) >>> 0) / 4294967296;
  };
}
var seed = 123456;
tracery.setRng(splitmix32(seed));
console.log(grammar.flatten('#origin#'));