title: How to get unique value of keys from array of object using javascript?
body: <p>I have an json data like this</p>
  
  <pre><code>{
    "name":"John",
    "age":30,
    "cars":"BMW"
  },
  {
    "name":"Micheal",
    "age":30,
    "cars":"Ford"
  },
  {
    "name":"Andy",
    "age":29,
    "cars":"Ford"
  }
  </code></pre>
  
  <p>I just want to get the unique value of cars in an array like this</p>
  
  <pre><code>cars = ["BMW, Ford"];
  </code></pre>