title: MongoDB Query for NON NULL fields
body: <p>I am working on a web scraping assignment and need to only show articles scraped that have a title, link, AND summary. </p>
  
  <p>If any of these are null I don't want to find them. This is my JS code:</p>
  
  <pre><code>results.link = $(element).find("a").attr("href");
  results.title = $(element).find("a").text().trim();
  results.summary = $(element).find("p.summary").text().trim();
  </code></pre>
  
  <p>I've tried variations of exists and type through mongo documentation but can't seem to pull the values I need. Any help is appreciated.</p>
  
  <pre><code>// Route for getting all Articles from the db
  app.get("/articles", function (req, res) {
    // Grab every document in the Articles collection that has a distinct title
    db.Article.distinct("results.title")
      .then(function (dbArticle) {
        // If we were able to successfully find Articles, send them back to the client
        res.json(dbArticle);
      })
      .catch(function (err) {
        // If an error occurred, send it to the client
        res.json(err);
      });
  });
  </code></pre>