title: Map an 'array of objects' to a simple array of key values
body: <p>I am new to the mongoDB aggregation pipeline and have a really basic question but could not find the answer anywhere. I would like to simply convert the following block:</p>
  
  <pre><code>"exclude" : [
              {
                  "name" : "Accenture"
              }, 
              {
                  "name" : "Aon Consulting"
              }
          ]
  </code></pre>
  
  <p>to:</p>
  
  <pre><code>"exclude" : [
              "Accenture",
              "Aon Consulting"
          ]
  </code></pre>
  
  <p>using the aggregation pipeline but I cannot seem to find how to do it even after going through the documentation on <a href="https://docs.mongodb.com/manual/reference/operator/aggregation/" rel="noreferrer">https://docs.mongodb.com/manual/reference/operator/aggregation/</a>. Thanks for your help.</p>