title: Sequelize: Append key value to Javascript collection
body: <p>Good morning everyone!</p>
  <p>I'm developing an application with Node.js and Angular, and I'm getting a little stuck lately.</p>
  <p>I need to append a <strong>custom key -&gt; value</strong> to an existing query result collection.</p>
  <p>This is the function I have:</p>
  <pre><code>exports.findAll = (req, res) =&gt; {
      Project.findAll({
              include: [{
                  all: true,
                  include: [{
                      all: true
                  }]
              }]
          })
          .then(data =&gt; {
              data.forEach(
                  (project) =&gt; {
                          // &lt;-------- HERE GOES THE APPEND
                  }
              );
              res.send(data);
          })
          .catch(err =&gt; {
              res.status(500).send({
                  message: err.message || &quot;Error retrieving projects&quot;
              });
          });
  };
  </code></pre>
  <p><strong>Description</strong>:</p>
  <p>After getting the result from the model query, I iterate over each result (aka Project).</p>
  <p>Then, what I need to do is <strong>append a key -&gt; value pair</strong> to that very Project.</p>
  <p>By now, I'd like to do something like this:</p>
  <pre><code>exports.findAll = (req, res) =&gt; {
      Project.findAll({
              include: [{
                  all: true,
                  include: [{
                      all: true
                  }]
              }]
          })
          .then(data =&gt; {
              data.forEach(
                  (project) =&gt; {
                      project.cat = &quot;miaw&quot;;
                  }
              );
              res.send(data);
          })
          .catch(err =&gt; {
              res.status(500).send({
                  message: err.message || &quot;Error retrieving projects&quot;
              });
          });
  };
  </code></pre>
  <p>This try hasn't made any changes in my JSON collection, and I don't know how to accomplish it neither.</p>
  <p>Could someone give me some help?
  I've searched everywhere but couldn't find anything useful.</p>
  <p>Thank you so much!</p>