title: access nested property using bracket notation
body: <p>Says I have <code>var input = {'name':'john'}</code></p>
  
  <p>I do 
  <code>input['name'] = 'James'</code></p>
  
  <p>it become <code>var input = {'name':'john'}</code> but can I pass value with dot to access nested property?</p>
  
  <p>Like</p>
  
  <p><code>var input = {"name":"john","grades":"{english:"A","math":"C"}"}</code></p>
  
  <p>I can't change the math value by doing <code>input["grades.math"]</code>.</p>