JavaScriptで類似度を計算する方法

function calc_tf(term, terms) {
  ct = 0;
  for (i in terms) {
    w = terms[i];
    if (w == term) {
      ct += 1;
    }
  }
  return ct / terms.length;
}

function calc_idf(term, texts) {
  ct = 0;
  for (i in texts) {
    terms = texts[i];
    if (terms.includes(term)) {
      ct += 1;
    }
  }
  if (ct == 0) {
    return 0;
  }
  result = Math.log(texts.length / ct) + 1;
  return result;
}

function calc_tfidf(word, words, texts) {
  tr = calc_tf(word, words);
  idf = calc_idf(word, texts);
  return tr * idf
}

function cosine_similarity(vector0, vector1) {
  // 類似度
  mykeys = Object.keys(vector0).concat(Object.keys(vector1));
  mykeys = Array.from(new Set(mykeys));
  a = [];
  for (i in mykeys) {
    k = mykeys[i];
    if (k in vector0) {
      a[k] = vector0[k];
    } else {
      a[k] = 0;
    }
  }

  b = [];
  for (i in mykeys) {
    k = mykeys[i];
    if (k in vector1) {
      b[k] = vector1[k];
    } else {
      b[k] = 0;
    }
  }
  x = 0;
  y = 0;
  z = 0;
  for (k in a) {
    u = a[k];
    v = b[k];
    x += u * v
    y += u ** 2
    z += v ** 2
  }
  if (y == 0 || z == 0) {
    return 0;
  }
  return x / (y ** (1 / 2)) / (z ** (1 / 2));
}

function calc_vector_tfidf(target_terms, texts) {
  v = [];
  for (i in target_terms) {
    target = target_terms[i];
    v[target] = calc_tfidf(target, target_terms, texts);
  }
  return v;
}

function get_similar_tfidf(target_terms, texts) {
  vector_target = calc_vector_tfidf(target_terms, texts);
  results = [];
  for (i in texts) {
    text = texts[i];
    vector_one = calc_vector_tfidf(text, texts);
    result = cosine_similarity(vector_target, vector_one);
    results.push([result, text]);
  }
  results.sort(function(a, b) {
    return b[0] - a[0];
  });
  return results;
}

target_terms = ["りんご", "みかん"];
texts = [
  ["りんご", "みかん"],
  ["りんご", "みかん", "みかん"],
  ["りんご", "みかん", "ばなな"],
  ["りんご", "ぶどう", "ばなな"],
  ["すいか", "ばなな"],
];
results = get_similar_tfidf(target_terms, texts)
console.log(results);