title: How to get all key in JSON object (javascript)
body: <pre><code>{"document":
    {"people":[
      {"name":["Harry Potter"],"age":["18"],"gender":["Male"]},
      {"name":["hermione granger"],"age":["18"],"gender":["Female"]},
    ]}
  }
  </code></pre>
  
  <p>From this JSON example, I would like to get the keys such as <code>name</code>, <code>age</code>, <code>gender</code> for each people.</p>
  
  <p>How to do this?</p>