title: Strange behavior of "delete" keyword in javascript
body: <p>I have an object "a" and I assign it to another variable named "b". 
  Now I delete some property values from "b" using delete keyword. It deletes that property from both objects "a" and "b". Why is that?</p>
  
  <p>P.S: I am beginner in javascript. go easy on me.</p>
  
  <p>Code: -</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>let a = {
    a:1,
    b:2,
    c:3
  }
  
  let b = a;
  console.log(a);   // output   { a: 1, b: 2, c: 3 }
  delete b.a;
  console.log(a)   // Expected output { a: 1, b: 2, c: 3 }    -- Actual output { b: 2, c: 3 }</code></pre>
  </div>
  </div>
  </p>