function getSharks() {
  var sharks = [];
  for (var i = 0; i < animals.length; i++) {
    if (animals[i].family === "Sharks") {
      sharks.push(animals[i]);
    }
  }
  return sharks;
}

SELECT * FROM animals WHERE family = 'Sharks';

<ul>
  <li class="selected">
    <p>Sharks</p>
    <ul>
      <li>Great White Shark</li>
      <li>Tiger Shark</li>
      <li>Hammerhead Shark</li>
    </ul>
  </li>
  <li>
    <p>Whales</p>
    <ul>
      <li>Blue Whale</li>
      <li>Humpback Whale</li>
      <li>Fin Whale</li>
    </ul>
  </li>
</ul>

li.selected > p {
  background-color: blue;
}

var liElements = document.getElementsByTagName("li");
for (var i = 0; i < liElements.length; i++) {
  if (liElements[i].className === "selected") {
    var children = liElements[i].childNodes;
    for (var j = 0; j < children.length; j++) {
      var child = children[j];
      if (child.nodeType === Node.ELEMENT_NODE && child.tagName === "P") {
        child.setAttribute("style", "background-color: blue");
      }
    }
  }
}

SELECT date_trunc('month', observation_timestamp) AS observation_month,
       sum(num_animals) AS total_animals
FROM observations
WHERE family = 'Sharks'
GROUP BY observation_month;

db.observations.mapReduce(
  function map() {
    var year = this.observationTimestamp.getFullYear();
    var month = this.observationTimestamp.getMonth() + 1;
    emit(year + "-" + month, this.numAnimals);
  },
  function reduce(key, values) {
    return Array.sum(values);
  },
  {
    query: { family: "Sharks" },
    out: "monthlySharkReport"
  }
);

db.observations.aggregate([
  { $match: { family: "Sharks" } },
  { $group: {
      _id: {
        year: { $year: "$observationTimestamp" },
        month: { $month: "$observationTimestamp" }
      },
      totalAnimals: { $sum: "$numAnimals" }
    }
  }
]);