crossover.js

const crossover = (individual1, individual2) => {
  // choose a random crossover point
  let point = Math.floor(Math.random() * NUM_CITIES);
  // create the offspring by combining the two individuals
  let offspring = individual1.slice(0, point).concat(individual2.slice(point));
  // remove duplicate cities from the offspring
  let uniqueCities = new Set(offspring);
  offspring = [...uniqueCities];
  // if the offspring is too short, add cities from the other individual
  if (offspring.length < NUM_CITIES) {
    for (let i = 0; i < NUM_CITIES; i++) {
      if (!offspring.includes(individual1[i])) {
        offspring.push(individual1[i]);
      }
    }
  }
  // return the offspring
  return offspring;
};